Miniaturized spectrometers for wearable devices

ABSTRACT

A method, system, apparatus, and/or device to determine a condition of a user using a wearable device with a miniaturized spectrometer. The method, system, apparatus, and/or device may include: a band configured to extend at least partially around a body part of a user, the body part comprising an internal feature within the body part; a light source embedded in the band, where the light source is configured to emit light into the body part as the user wears the band; a collimator; an optical filter; and an optical sensor, where the collimator, optical sensor, or the optical filter are arranged together to form a stack embedded in the band.

BACKGROUND

Spectral or optical spectroscopy is the analysis of the emission,absorption, and reflection of light by matter. Different types of matterabsorb and reflect light differently. For example, a spectral analysisof living tissue can be used to detect various forms of cancer and othertypes of diseases. In this example, spectral analysis includesilluminating a tissue region under examination with light and using alight detector to detect and analyze the optical properties of theilluminated tissue region by measuring light energy modified by itsinteraction with the tissue region. In this example, the diseased tissuemay be identified by comparing the optical properties of normal tissuewith the optical properties of disease tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

The present description will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the present embodiment, which description is not to betaken to limit the present embodiment to the specific embodiments butare for explanation and understanding. Throughout the description thedrawings may be referred to as drawings, figures, and/or FIGs.

FIG. 1 illustrates a wearable device with integrated sensors, accordingto an embodiment.

FIG. 2A illustrates a top exposed view of the wearable device describedand illustrated regarding FIG. 1, according to an embodiment.

FIG. 2B illustrates a profile view of the wearable device, according toan embodiment.

FIG. 2C illustrates a side view of the wearable device, according to anembodiment.

FIG. 3A illustrates the wearable device attached to a part of a body ofan individual, according to an embodiment.

FIG. 3B illustrates the wearable device with the second sensor beinglocated approximate the first muscular-walled tube and the light sourceand the first sensor being located approximate the secondmuscular-walled tube, according to an embodiment.

FIG. 3C illustrates the wearable device with the second sensor beinglocated approximate the second muscular-walled tube and the light sourceand the first sensor being located approximate the first muscular-walledtube, according to an embodiment.

FIG. 3D illustrates the wearable device with the light source, the firstsensor, and the second sensor being located longitudinally andapproximate the first muscular-walled tube, according to an embodiment.

FIG. 3E illustrates the wearable device with the light source, the firstsensor, and the second sensor being located laterally and approximatethe first muscular-walled tube, according to an embodiment.

FIG. 3F illustrates the wearable device with the light source, the firstsensor, and the second sensor being located in parallel and approximatethe first muscular-walled tube, according to an embodiment.

FIG. 3G illustrates the wearable device with the light source and thefirst sensor being located approximate the first muscular-walled tubeand the second sensor being located approximate the secondmuscular-walled tube, according to an embodiment.

FIG. 3H illustrates the wearable device with the light source and thefirst sensor being located approximate the second muscular-walled tubeand the second sensor being located approximate the firstmuscular-walled tube, according to an embodiment.

FIG. 3I illustrates a zoomed-in view of the wearable device, focusing inon the first sensor, the light source, and the first muscular-walledtube, with the light source positioned over the first muscular-walledtube, according to an embodiment.

FIG. 3J illustrates a zoomed-in view of the wearable device similar toFIG. 3I, with the first sensor positioned over the first muscular-walledtube, according to an embodiment.

FIG. 4 illustrates a view of a wearable device around a body part with alight source emitting light through the body part to a sensor, accordingto an embodiment.

FIG. 5A illustrates a perspective view of a first sensor, according toan embodiment.

FIG. 5B illustrates a transmission profile of a filter which may beincorporated into the first sensor, according to an embodiment.

FIG. 5C illustrates a side view of the first sensor, according to anembodiment.

FIG. 5D illustrates an embodiment of the first sensor with themicrotubes aligned directly with filter regions, according to anembodiment.

FIG. 6A illustrates a cross-sectional view of a light source emittinglight rays into a first sensor, according to an embodiment.

FIG. 6B illustrates a perspective cross-sectional view of the lightsource emitting the light rays into the first sensor, according to anembodiment.

FIG. 6C illustrates a plurality of the light source positioned adjacentto regions of a filter, according to an embodiment.

FIG. 7A illustrates an embodiment of a collimator arranged in a firsttwo-dimensional array of cylindrical microtubes, according to anembodiment.

FIG. 7B illustrates an embodiment of a collimator arranged in a secondtwo-dimensional array, including square microtubes, according to anembodiment.

FIG. 7C illustrates an embodiment of a collimator arranged in a thirdtwo-dimensional array, including the square microtubes illustrated inFIG. 7B, according to an embodiment.

FIG. 8 illustrates an embodiment of the collimator illustrated in FIG.7B, further including a filler, according to an embodiment.

FIG. 9A illustrates a ray diagram of light passing through one or morelayers of a miniaturized spectrometer, according to an embodiment.

FIG. 9B illustrates a ray diagram showing a shadow effect of thecollimator on light passing through the miniaturized spectrometer,according to an embodiment.

FIG. 10A illustrates a ray diagram that correlates a gap between acollimator and an optical sensor of a miniaturized spectrometer with aregion on the optical sensor light may impinge, according to anembodiment.

FIG. 10B illustrates a ray diagram that correlates a gap between afilter and an optical sensor of a miniaturized spectrometer with theregion on the optical sensor light may impinge, according to anembodiment.

FIG. 10C illustrates an orientation and structure of a collimatorrelative to a filter that may reduce and/or eliminate crossing of lightto a neighboring sensor segment, according to an embodiment.

FIG. 11A is a picture of a section of a collimator, according to anembodiment.

FIG. 11B illustrates a side view of a cross-section of a wall of acollimator, showing an internal structure of the wall, according to anembodiment.

FIG. 11C illustrates a picture from a perspective view of the collimator530, according to an embodiment.

FIG. 12A is a top-side picture of the collimator showing the wall andthe through-channel of the microtube, according to an embodiment.

FIG. 12B is a picture of a diffraction pattern of light collimated by acollimator at 10 mm from the collimator, according to an embodiment.

FIG. 13 shows a graph 1300 illustrating an intensity profile of thediffraction pattern 1200 illustrated in FIG. 12B

FIG. 14A shows a graph illustrating transmission curves corresponding tovarious refractive indices for collimated and uncollimated light,according to an embodiment.

FIG. 14B shows a graph illustrating transmission curves corresponding tovarious through-channel widths for collimated light, according to anembodiment.

FIG. 15A is a graph illustrating a transmission efficiency of amicrotube having a wall with a 250 micrometer (micron) height and athrough-channel with a 25-micron width, according to an embodiment.

FIG. 15B is a graph illustrating a transmission efficiency of amicrotube having a wall with a 250-micron height and a through-channelwith a 50 micron width, according to an embodiment.

FIG. 15C is a graph illustrating a transmission efficiency of amicrotube having a wall with a 250-micron height and a through-channelwith a 100 micron width, according to an embodiment.

DETAILED DESCRIPTION

A miniaturized spectrometer as disclosed herein will become betterunderstood through a review of the following detailed description inconjunction with the figures. The detailed description and figuresprovide merely examples of the various embodiments described herein.Those skilled in the art will understand that the disclosed examples maybe varied, modified, and altered and not depart from the scope of theembodiments described herein. Many variations are contemplated fordifferent applications and design considerations; however, for the sakeof brevity, the contemplated variations may not be individuallydescribed in the following detailed description.

Throughout the following detailed description, examples of variousminiaturized spectrometers are provided. Related features in theexamples may be identical, similar, or dissimilar in different examples.For the sake of brevity, related features will not be redundantlyexplained in multiple examples. Instead, the use of a same, similar,and/or related element names and/or reference characters may cue thereader that an element with a given name and/or associated referencecharacter may be similar to another related element with the same,similar, and/or related element name and/or reference character in anexample embodiment explained elsewhere herein. Elements specific to agiven example may be described regarding that particular exampleembodiment. A person having ordinary skill in the art will understandthat a given element need not be the same or similar to the specificportrayal of a related element in any given figure or example embodimentin order to share features of the related element.

As used herein “same” means sharing all features and “similar” meanssharing a substantial number of features or sharing materially importantfeatures even if a substantial number of features are not shared. Asused herein “may” should be interpreted in the permissive sense andshould not be interpreted in the indefinite senses. Additionally, anduse of “is” regarding embodiments, elements, and/or features should beinterpreted to be definite only regarding a specific embodiment andshould not be interpreted as definite regarding the invention as awhole.

Where multiples of a particular element are shown in a FIG., and whereit is clear that the element is duplicated throughout the FIG., only onelabel may be provided for the element, despite multiple instances of theelement being present in the FIG. Accordingly, other instances in theFIG. of the element having identical or similar structure and/orfunction may not have been redundantly labeled. A person having ordinaryskill in the art will recognize based on the disclosure herein redundantand/or duplicated elements of the same FIG. Despite this, redundantlabeling may be included where helpful in clarifying the structure ofthe depicted example embodiments.

A spectral or optical spectrometer is an optical instrument formeasuring and examining the spectral characteristics of the input lightover an electromagnetic spectrum. A conventional optical spectrometermay include a light source, a collimator, a wavelength selector, and adetector. The conventional optical spectrometer may include an entranceslit through which optical beams are fed into the spectrometer. Inconventional spectrometers, to maximize the throughput efficiency, theapertures of the optical elements within the spectrometer must be largeenough to accept full optical beams without truncation in order to havea three-dimensional propagation path. The detector converts opticalsignals to electronic signals. However, all the parts of theconventional spectrometer combine into a cumbersome and complexstructure that is large in body volume and heavy in weight. Thestructure of the conventional spectrometer limits the minimum size andweight of the spectrometer because the structure requires a minimumamount of distance between the parts of the spectrometer to allow thelight to be properly dispersed into different wavelengths for analysis.A conventional spectrometer may include a lens that may collimate lightdirected to a photodetector in the spectrometer. The lens may haveastigmatism which may limit an intensity of collimated light strikingthe detector and/or may limit the ability of the spectrometer toseparate light into distinct wavelengths. Furthermore, as the structureof the conventional spectrometer is reduced in size and volume, thefidelity and resolution of the spectral analysis decreasesexponentially.

Implementations of the disclosure address the above-mentioneddeficiencies and other deficiencies by providing methods, systems,devices, or apparatuses to measure and examine the spectralcharacteristics of the light over an electromagnetic spectrum. In oneembodiment, the miniaturized spectrometer may include a light source, anano-collimator, a miniaturized wavelength selector, and a miniaturizeddetector. The miniaturized spectrometer may include a carbon nanotube(CNT) collimator that is on a nanoscale. The light source may emit lightincluding one or more wavelengths. The miniaturized spectrometer may beintegrated into a wearable device. For example, the miniaturizedspectrometer may be integrated into a wristband of a wearable device.The wearable device may include a watch, and the miniaturizedspectrometer may be integrated into a band of the watch. Theminiaturized spectrometer may be configured to continuously orsemi-continuously measure and examine the spectral characteristics ofthe light over an electromagnetic spectrum. The light may pass directlyfrom the light source to the detector or may pass indirectly through asubstance and be reflected towards the detector. An advantage of theminiaturized spectrometer is a simplified optical system that is reducedin body volume and weight while maintaining high fidelity and resolutionof the optical characteristics of the detected light. Another advantageof the miniaturized spectrometer is to provide a spectrometer that maybe integrated into portable electronic devices to provide ease of use.Another advantage of the miniaturized spectrometer is to provide aportable spectrometer that may be used to continuously orsemi-continuously monitor light.

FIG. 1 illustrates a wearable device 100 with integrated sensors 112and/or 114, according to an embodiment. The elements and/or featuresdescribed regarding FIG. 1 may be the same as and/or similar to othersimilarly named elements and/or features described and/or illustratedthroughout this disclosure. In one embodiment, the wearable device 100may be configured to take physiological measurements of a user. Thewearable device 100 may include a housing 118 and an attachmentmechanism 106, such as a band, that are configured or shaped to attachto a body of the user. In one embodiment, the wearable device 100 may bea wrist worn device that may be configured to attach to a wrist or armof the user. In one example, the integrated sensors 112 and/or 114 maybe positioned against an inside region of the wrist when the user wearsthe wearable device 100. The inside region of the wrist may face towardsthe user in a natural resting position. In another example, when theintegrated sensors 112 and/or 114 may be positioned against an insideregion of the body part, such as the wrist, the integrated sensors 112and/or 114 may be positioned adjacent to, approximate to, or directlyover a muscular-walled tube that is closest to an outer surface of thebody part. In another embodiment, the wearable device 100 may beattached to a head of the user using a headband, to a chest of the userusing a chest band, to an ankle of the user using an ankle band, orotherwise attached to a body of the user using a sweatband, bandage,band, watch, bracelet, ring, adherent, or other attachments andconnections.

In various embodiments, the housing 118 may be moveably coupled to theband 106. In one example, the band 106 may be a flexible band designedto flex into a curvilinear shape. The flexible band with a shape, size,and/or flexibility designed for attaching the band 106 to a wrist of auser. The wrist may include a dermal layer along an underside of thewrist and a muscular-walled tube within the wrist adjacent to the dermallayer along the underside of the wrist. The housing 118 may beconfigured with external electrical contacts. The band 106 may beconfigured with multiple contact points or a continuous contact strip.The housing 118 may be coupled to the band 106 such that the externalelectrical contacts of the housing 118 form electrical contact with theone or more of the multiple contact points or the continuous contactstrip of the band 106. The housing 118 may be moved on the band 106 to adifferent position and still maintain electrical communication withelectrical components embedded in the band 106 such as the electricaltrace or circuit 116, the first sensor 112, or the second sensor 114.

The wearable device 100 may include a processing device 102, a userinterface or display device 104, the band 106, a power source 108, aprocessing unit 110, the first sensor 112, and/or the second sensor 114.In one embodiment, the processing device 102, the user interface ordisplay device 104, the power source 108, the processing unit 110, thefirst sensor 112, and/or the second sensor 114 may be electronicallycoupled and/or communicatively coupled. In another embodiment, theprocessing device 102 and the display device 104 may be integrated intothe housing 118 of the wearable device 100. In another embodiment, thepower source 108, the processing unit 110, the first sensor 112, and/orthe second sensor 114 may be integrated into the band 106 of thewearable device 100. In one embodiment, the first sensor 112 and/or thesecond sensor 114 may be integrated or positioned along an insidesurface or interior surface of the band 106, such that the first sensor112 and/or the second sensor 114 may be flush with the surface of theband 106 to contact a body part of a user when worn or protrude from asurface of the band 106 to extend toward a surface of the body part ofthe user when worn. In another embodiment, the band 106 may include acavity that the power source 108, the processing unit 110, the firstsensor 112, and/or the second sensor 114 may be stored in. In anotherembodiment, the band 106 may be formed or molded over the power source108, the processing unit 110, the first sensor 112, and/or the secondsensor 114. In another embodiment, the power source 108, the firstsensor 112, and/or the second sensor 114 may be connected to theprocessing unit 110 and/or the processing device 102 by one or moreelectrical trace(s) or circuit(s) 116 (such as flexible circuit boards).

In one embodiment, the first sensor 112 may be a miniaturizedspectrometer. The miniaturized spectrometer may include acarbon-nanotube structure forming a collimator, an optical filter, and aphotodetector stacked together and embedded in the band 106. Thephotodetector may be positioned in the band 106 to face the user's bodypart 320 when the user wears the band 106. In another embodiment, thesecond sensor 114 may be a miniaturized impedance sensor. In anotherembodiment, the first sensor 112 and/or the second sensor may be atemperature sensor, a viscosity sensor, an ultrasonic sensor, a humiditysensor, a heart rate sensor, a dietary intake sensor, anelectrocardiogram (EKG) sensor, an ECG sensor, a galvanic skin responsesensor, a pulse oximeter, an optical sensor, and so forth. In anotherembodiment, the wearable device 100 may include other sensors integratedor attached to the band 106 or the housing 118. In another embodiment,the wearable device 100 may be communicatively coupled to the wearabledevice 100, such as sensors of other devices or third-party devices.

The first sensor 112 and/or the second sensor 114 may be coupled to theprocessing unit 110. The processing unit 110 may be configured to manageor control the first sensor 112, the second sensor 114, and/or the powersource 108. In one embodiment, the processing unit 110 may control afrequency or rate over time that the first sensor 112 and/or the secondsensor 114 take measurements, a wavelength or optical frequency at whichthe first sensor 112 and/or the second sensor 114 take measurements, apower consumption level of the first sensor 112 and/or the second sensor114, a sleep mode of the first sensor 112 and/or the second sensor 114and so forth. In another embodiment, the processing unit 110 may controlor adjust measurements taken by the first sensor 112 and/or the secondsensor 114 take measurements to remove noise, increase a signal to noiseratio, dynamically adjust the amount of measurements taken over time,and so forth.

In another embodiment, the power source 108 may be coupled to theprocessing unit 110. The power source 108 may be a battery, a solarpanel, a kinetic energy device, a heat converter power device, awireless power receiver, and so forth. The processing unit 110 may beconfigured to transfer power from the power source 108 to the processingdevice 102, the display device 104, the first sensor 112, the secondsensor 114, and/or other devices or units of the wearable device 100. Inone embodiment, the processing unit 110 may be configured to regulate anamount of power provided from the power source 108 to the processingdevice 102, the display device 104, the first sensor 112, the secondsensor 114, and/or other devices or units of the wearable device 100. Inanother embodiment, the wearable device 100 may include a power receiverto receive power to recharge the power source 108. For example, thepower receiver may be a wireless power coil, a universal serial bus(USB) connector, a thunderbolt connector, a mini USB connector, a microUSB connector, a USB-C connector, and so forth. The power receiver maybe coupled to the processing unit 110, the processing device 102, thepower source 108, and so forth. In one embodiment, the processing unit110 may be configured to regulate an amount of power provided from thepower receiver to the power source 108. In another embodiment, theprocessing unit 110 may be a power management unit configured to controlbattery management, voltage regulation, charging functions, directcurrent (DC) to DC conversion, voltage scaling, power conversion,dynamic frequency scaling, pulse-frequency modulation (PFM), pulse-widthmodulation (PWM), amplification, and so forth. In another embodiment,the processing unit 110 may include a communication device configured tosend and/or receive data via a cellular communication channel, awireless communication channel, a Bluetooth® communication channel, aradio communication channel, a WiFi® communication channel, and soforth.

The processing device 102 may include a processor, a data storagedevice, a communication device, a graphics processor, and so forth. Inone embodiment, the processing device 102 may be coupled to theprocessing unit 110, the power source 108, the first sensor 112, and/orthe second sensor 114. In one embodiment, the processing device 102 maybe configured to receive measurement data from the processing unit 110,the first sensor 112, and/or the second sensor 114. In one embodiment,the processing device 102 may be configured to process the measurementdata and display information associated with the measurement data at thedisplay device 104. In another embodiment, the processing device 102 maybe configured to communicate the measurement data to another device. Inone embodiment, the other device may process the measurement data andprovide information associated with the measurement data to the user oranother individual. In another embodiment, the other device may processthe measurement data and provide results, analytic information,instructions, and/or notifications to the processing device 102 toprovide to the user. The wearable device 100 may communicate informationassociated with the measurement data or information related to themeasurement data to a user via the display device 104, a buzzer, avibrator, a speaker, a microphone, and so forth. In one example, thedisplay device 104 may include an input device, such as a button, atouch screen, a touch display, an so forth that may receive an inputform the user.

In another embodiment, the wearable device 100 may be part of a systemconnected to other devices. For example, the wearable device 100 may beconfigured to send and/or receive data with another device. In oneembodiment, the wearable device 100 may be configured to receive datafrom another measurement device, aggregate the received data withmeasurement data from the first sensor 112 and/or the second sensor 114,analyze the aggregated data, and provide information or notificationsassociated with the analyzed data.

FIGS. 2A-C illustrate side and top views of a wearable device 100,according to an embodiment. FIG. 2A illustrates a top exposed view ofthe wearable device 100 in FIG. 1, according to an embodiment. Some ofthe features in FIG. 2A are the same as or similar to some of thefeatures in FIG. 1 as noted by same and/or similar reference characters,unless expressly described otherwise. Furthermore, the elements and/orfeatures described regarding FIG. 2A may be the same as and/or similarto other similarly named elements and/or features described and/orillustrated throughout this disclosure. As discussed above, the wearabledevice 100 may be a wrist-worn device that may be configured to attachto a wrist of a user. As further discussed above, the processing device102 and the display device 104 may be integrated into the housing 118 ofthe wearable device 100 and the power source 108, the processing unit110, the first sensor 112, and/or the second sensor 114 may beintegrated into the band 106 of the wearable device 100. In oneembodiment, the band 106 may include a cavity that the power source 108,the processing unit 110, the first sensor 112, and/or the second sensor114 may be stored in. In another embodiment, the band 106 may be formedor molded over the power source 108, the processing unit 110, the firstsensor 112, and/or the second sensor 114. In various embodiments, theband 106 may be formed of silicone and/or canvas material.

FIG. 2B illustrates a profile view of the wearable device 100, accordingto an embodiment. Some of the features in FIG. 2B are the same as orsimilar to some of the features in FIG. 1 and FIG. 2A as noted by sameand/or similar reference characters, unless expressly describedotherwise. Furthermore, the elements and/or features described regardingFIG. 2B may be the same as and/or similar to other similarly namedelements and/or features described and/or illustrated throughout thisdisclosure. In one embodiment, the housing 118 with the processingdevice 102 and the display device 104 (as shown in FIGS. 1 and 2A) maybe located at a top of the wearable device 100 such that the housing 118may be located at a top surface of a wrist of a user when the user wearsthe wearable device 100 on their wrist. In another embodiment, the firstsensor 112 and/or the second sensor 114 (as shown in FIGS. 1 and 2A) maybe located at a bottom of the wearable device 100 such that the firstsensor 112 and/or the second sensor 114 may be located at a bottomsurface of a wrist of a user when the user wears the wearable device 100on their wrist. In another embodiment, the power source 108 and/or theprocessing unit 110 (as shown in FIGS. 1 and 2A) may be located along aside of the wearable device 100 such that the power source 108 and/orthe processing unit 110 may be located at a side surface of a wrist of auser when the user wears the wearable device 100 on their wrist.

FIG. 2C illustrates a side view of the wearable device 100, according toan embodiment. Some of the features in FIG. 2C are the same or similarto some of the features in FIGS. 1-2B as noted by same referencecharacters, unless expressly described otherwise. As discussed above,the wearable device 100 may include the power source 108, the processingunit 110, the first sensor 112, and/or the second sensor 114. In anotherembodiment, the power source 108, the first sensor 112, and/or thesecond sensor 114 may be connected to the processing unit 110 and/or theprocessing device 102 by one or more electrical trace(s) or circuit(s)116. In one embodiment, the electrical trace 116 may extend at leastpartially along a circumference of the band 106. In one embodiment, thepower source 108 may be located on one or both sides of the band 106,the first sensor 112 and/or the second sensor 114 may be located at abottom of the band, and the processing unit 110 may be located at a sideor a top of the band 106 (such as approximate the housing 118). In oneembodiment, the electrical trace(s) 116 may extend along a circumferenceof the band 106 along a side or middle circumference of the band 106.The electrical trace(s) 116 may transfer data and/or power between thepower source 108, the first sensor 112, the second sensor 114, theprocessing unit 110, the processing device 102 (as shown in FIG. 1),and/or the display device 104 (as shown in FIG. 1).

FIGS. 3A-H illustrate various embodiments of the wearable device 100positioned on a user relative to veins and/or arteries of the user,according to various embodiments. FIG. 3A illustrates the wearabledevice 100 attached to a part of a body 320 of an individual, accordingto an embodiment. Some of the features in FIG. 3A are the same as orsimilar to some of the features in FIGS. 1-2B as noted by same and/orsimilar reference characters, unless expressly described otherwise.Furthermore, the elements and/or features described regarding FIG. 3Amay be the same as and/or similar to other similarly named elementsand/or features described and/or illustrated throughout this disclosure.In one embodiment, the wearable device 100 may be attached to the partof the body 320 of the individual. The part of the body 320 may be anarm, a leg, a hand, a wrist, a head, an appendage, and so forth of thebody 320 of the individual. For example, the wearable device 100 may beattached to a wrist or arm of the body 320 of the individual. Asdiscussed above, the wearable device 100 may include the first sensor112 and/or the second sensor 114. In another embodiment, the firstsensor 112 and or the second sensor 114 may be attached to a band of thewearable device 100 such that the first sensor 112 and/or the secondsensor 114 may be aligned over a muscular-walled tube 322 and/or 324 ofthe body 320 of the individual. The muscular-walled tube 322 and/or 324may be a vein, an artery, or other tubes or channels to circulate fluidsin the body 320, such as blood, water, oxygen, and so forth. Forexample, the first muscular-walled tube 322 may be an ulnar artery orvein and the second muscular-walled tube 324 may be a radial artery orvein.

In one embodiment, the wearable device 100 may include one or more lightsources 326 integrated into the band of the wearable device 100 suchthat the light sources 326 are offset to a first side of the firstmuscular-walled tube 322 and extend horizontally along surface of theskin offset to the muscular-walled tube 322. The light source(s) 326 maybe light emitting diodes (LEDs), incandescent bulbs, tungsten bulbs,lasers, and so forth. In one embodiment, the wearable device 100 mayinclude the first sensor 112 integrated into the band of the wearabledevice 100 such that the first sensor 112 may be offset to a second sideof the muscular-walled tube 322 and extend horizontally along surface ofthe skin offset to the muscular-walled tube 322. In one embodiment, thelight sources 326 may be located at a first side of the muscular-walledtube 322 and the first sensor 112 may be located opposite to the lightsources 326 on the other side of the muscular-walled tube 322. Inanother embodiment, the second sensor 114 may be a miniaturizedimpedance sensor that may be positioned over top of the muscular-walledtube 322. The muscular-walled tube may include a blood vessel such as avein or artery in an arm or wrist of a body 320 of the user, such as ahuman body. In one embodiment, the second sensor 114 may be integratedinto the band of the wearable device 100 such that the second sensor 114may run parallel to and extend horizontally along surface of the skinabove the muscular-walled tube 322.

The first sensor 112 and the second sensor 114 may be compactly arrangedin the wearable device 100. The close proximity of the first sensor 112,the second sensor 114, and/or the light source 326 may reduce an amountof wiring disbursed throughout the wearable device 100. The first sensor112, the second sensor 114, and/or the light source 326 may beintegrated into and/or on a single substrate. The substrate may beflexible and/or rigid. Compact arrangement of the sensors may allow foruse of a rigid substrate, which may increase the durability of thesensors and/or the wearable device 100 overall. Compact arrangement ofthe sensor may also allow for consistency of measurement. In variousembodiments, such as embodiments discussed regarding FIG. 26,measurements of multiple sensors may be correlated and/or aggregated.Compact arrangement may allow for measurement by multiple sensors of thesame muscular-walled tube 322 at the same or roughly the same locationon the muscular-walled tube. This may increase the precision ofcorrelations and/or aggregations.

FIG. 3B illustrates the wearable device 100 with the second sensor 114being located approximate the first muscular-walled tube 322 and thelight source 326 and the first sensor 112 being located approximate thesecond muscular-walled tube 324, according to an embodiment. Some of thefeatures in FIG. 3B are the same as or similar to some of the featuresin FIGS. 1-3A as noted by same and/or similar reference characters,unless expressly described otherwise. Furthermore, the elements and/orfeatures described regarding FIG. 3B may be the same as and/or similarto other similarly named elements and/or features described and/orillustrated throughout this disclosure. In one embodiment, the secondsensor 114 may be located over the first muscular-walled tube 322. Inone embodiment, the second sensor 114 may include a miniaturizedimpedance sensor. In one embodiment, the first muscular-walled tube 322may extend along a Y-axis of a first plane and the miniaturizedimpedance sensor may extend perpendicularly relative to the firstmuscular-walled tube 322 along an X-axis of a second plane, such thatthe miniaturized impedance sensor extends from a first side of the firstmuscular-walled tube 322 to a second side of the first muscular-walledtube 322. In another embodiment, the first sensor 112 may be located ata first side of the second muscular-walled tube 324 and the lightsource(s) 326 may be located on a second side of the secondmuscular-walled tube 324, such that the first sensor 112 and the lightsource(s) 326 straddle each side of second muscular-walled tube 324.

FIG. 3C illustrates the wearable device 100 with the second sensor 114being located approximate the second muscular-walled tube 324 and thelight source 326 and the first sensor 112 being located approximate thefirst muscular-walled tube 322, according to an embodiment. Some of thefeatures in FIG. 3C are the same as or similar to some of the featuresin FIGS. 1-3B as noted by same and/or similar reference characters,unless expressly described otherwise. Furthermore, the elements and/orfeatures described regarding FIG. 3C may be the same as and/or similarto other similarly named elements and/or features described and/orillustrated throughout this disclosure. In one embodiment, the secondsensor 114 may be located over the second muscular-walled tube 324. Inone embodiment, the second sensor 114 may include a miniaturizedimpedance sensor. In one embodiment, the second muscular-walled tube 324may extend along a Y-axis of a first plane and the miniaturizedimpedance sensor may extend perpendicularly relative to the secondmuscular-walled tube 324 along an X-axis of a second plane, such thatthe miniaturized impedance sensor may extend from a first side of thesecond muscular-walled tube 324 to a second side of the secondmuscular-walled tube 324. In another embodiment, the first sensor 112may be located at a first side of the first muscular-walled tube 322 andthe light source(s) 326 may be located on a second side of the firstmuscular-walled tube 322, such that the first sensor 112 and the lightsource(s) 326 straddle each side of first muscular-walled tube 322.

The embodiments illustrated in FIGS. 3B-C generally illustrateembodiments where the first sensor 112 is placed to take measurementsnear and/or from one muscular-walled tube, and the second sensor 114 isplaced to take measurements near and/or from another muscular-walledtube. The two muscular-walled tubes may have different featurescorresponding to different physiological conditions, physiologicalparameters, and/or physiological constituents. The two muscular-walledtubes may have different features corresponding to a change in aphysiological condition, physiological parameter, and/or physiologicalconstituent. For example, one of the muscular-walled tubes may be avein, and the other muscular-walled tube may be an artery. In general,arteries may carry oxygenated blood, and veins may carry deoxygenatedblood. In the embodiments illustrated in FIGS. 3B-C, the arrangements ofthe sensor may allow for correlation of oxygenated blood to deoxygenatedblood. This in turn may inform a determination of a physiologicalcondition, physiological parameter, and/or physiological constituent ofa user of the wearable device 100. For example, the wearable device 100may include the processing unit 110, which may correlate measurementstaken by the first sensor 112 and the second sensor 114 placed over thefirst muscular-walled tube 322 and the second muscular-walled tube 324,respectively, to determine that the blood is not being sufficientlyoxygenated.

FIG. 3D illustrates the wearable device 100 with the light source 326,the first sensor 112, and the second sensor 114 being locatedlongitudinally and approximate the first muscular-walled tube 322,according to an embodiment. Some of the features in FIG. 3D are the sameas or similar to some of the features in FIGS. 1-3C as noted by sameand/or similar reference characters, unless expressly describedotherwise. Furthermore, the elements and/or features described regardingFIG. 3D may be the same as and/or similar to other similarly namedelements and/or features described and/or illustrated throughout thisdisclosure. In one embodiment, the first sensor 112 may be located at afirst side of a first location along the first muscular-walled tube 322and the light source(s) 326 may be located on a second side of the firstlocation along the first muscular-walled tube 322, such that the firstsensor 112 and the light source(s) 326 straddle each side of the firstlocation along the first muscular-walled tube 322. In anotherembodiment, the second sensor 114 may be located over a second locationalong the first muscular-walled tube 322. In another embodiment, thesecond sensor 114 may include a miniaturized impedance sensor. In oneembodiment, the first muscular-walled tube 322 may extend along a Y-axisof a first plane and the miniaturized impedance sensor may extendperpendicularly relative to the first muscular-walled tube 322 along anX-axis of a second plane, such that the miniaturized impedance sensormay extend from a first side of the first muscular-walled tube 322 to asecond side of the first muscular-walled tube 322. In one embodiment,the first location along the first muscular-walled tube 322 may belocated above or ahead of the second location along the firstmuscular-walled tube 322 along the Y-axis. In another embodiment, thefirst location along the first muscular-walled tube 322 may be locatedbelow or behind of the second location along the first muscular-walledtube 322 along the Y-axis.

FIGS. 3A-D generally show the second sensor 114 aligned with its lengthparallel to the length of the muscular-walled tubes. Parallel alignmentof the second sensor 114 to the muscular-walled tubes may allow formeasurements and/or characterization of features running parallel to thelength of the muscular-walled tubes. For example, in embodiments wherethe second sensor 114 includes the miniaturized impedance sensor, thecurrent passed into the user by the miniaturized impedance sensor mayrun parallel or roughly parallel to the length of the muscular-walledtube to which the miniaturized impedance sensor corresponds. In anembodiment where the muscular-walled tube includes a vein or artery,parallel alignment of the miniaturized impedance sensor may allow formeasurement and/or characterization of the blood in the vein or arteryalong a path of the blood in the vein or artery. Similarly, parallelalignment of the miniaturized impedance sensor may allow for measurementand/or characterization of the muscular-walled tube along the length ofthe muscular-walled tube.

FIG. 3E illustrates the wearable device 100 with the light source 326,the first sensor 112, and the second sensor 114 being located laterallyand approximate the first muscular-walled tube 322, according to anembodiment. Some of the features in FIG. 3E are the same as or similarto some of the features in FIGS. 1-3D as noted by same and/or similarreference characters, unless expressly described otherwise. Furthermore,the elements and/or features described regarding FIG. 3E may be the sameas and/or similar to other similarly named elements and/or featuresdescribed and/or illustrated throughout this disclosure. In oneembodiment, the first sensor 112 may be located at a first side of alocation along the first muscular-walled tube 322 and the lightsource(s) 326 may be located on a second side of the location along thefirst muscular-walled tube 322, such that the first sensor 112 and thelight source(s) 326 may straddle each side of the first location alongthe first muscular-walled tube 322. In another embodiment, the secondsensor 114 may be located over the same location along the firstmuscular-walled tube 322. In another embodiment, the second sensor 114may include a miniaturized impedance sensor. In one embodiment, thelight source 326, the first sensor 112, and the second sensor 114 mayextend laterally along the X-axis and perpendicularly to themuscular-walled tube 322. In one embodiment, the second sensor 114 maybe located between the light source 326 and the first sensor 112. Inanother embodiment, the second sensor 114 may be located at an exteriorside of the light source 326 or the first sensor 112. In anotherembodiment, a first portion of the second sensor 114 may be located atan exterior side of the light source 326 and a second portion of thesecond sensor 114 may be located at an exterior side of the first sensor112.

Perpendicular alignment of the second sensor 114 to the muscular-walledtubes may allow for measurements and/or characterization of featuresrunning perpendicular to the length of the muscular-walled tubes. Forexample, in embodiments where the second sensor 114 includes theminiaturized impedance sensor, the current passed into the user by theminiaturized impedance sensor may run perpendicular or roughlyperpendicular to the length of the muscular-walled tube to which theminiaturized impedance sensor corresponds. In an embodiment where themuscular-walled tube includes a vein or artery, perpendicular alignmentof the miniaturized impedance sensor may allow for measurement and/orcharacterization of a cross-sectional area of the blood in the vein orartery. Similarly, perpendicular alignment of the miniaturized impedancesensor may allow for measurement and/or characterization of themuscular-walled tube along the circumference and/or diameter of themuscular-walled tube.

FIG. 3F illustrates the wearable device 100 with the light source 326,the first sensor 112, and the second sensor 114 being located inparallel and approximate the first muscular-walled tube 322, accordingto an embodiment. Some of the features in FIG. 3F are the same as orsimilar to some of the features in FIGS. 1-3E as noted by same and/orsimilar reference characters, unless expressly described otherwise.Furthermore, the elements and/or features described regarding FIG. 3Fmay be the same as and/or similar to other similarly named elementsand/or features described and/or illustrated throughout this disclosure.In one embodiment, the first sensor 112 may be located at a first sideof a first location along the first muscular-walled tube 322 and thelight source(s) 326 may be located on a second side of the firstlocation along the first muscular-walled tube 322, such that the firstsensor 112 and the light source(s) 326 may straddle each side of thefirst location along the first muscular-walled tube 322. In anotherembodiment, the second sensor 114 may be located over a second locationalong the first muscular-walled tube 322. In another embodiment, thesecond sensor 114 may include a miniaturized impedance sensor. In oneembodiment, the first muscular-walled tube 322 may extend along a Y-axisof a first plane and the impedance pad(s) may extend parallel to thefirst muscular-walled tube 322 along a Y-axis of a second plane, suchthat the impedance pad(s) extend along a portion of the firstmuscular-walled tube 322. In one embodiment, the first location alongthe first muscular-walled tube 322 may be located above or ahead of thesecond location along the first muscular-walled tube 322 along theY-axis. In another embodiment, the first location along the firstmuscular-walled tube 322 may be located below or behind of the secondlocation along the first muscular-walled tube 322 along the Y-axis.

FIG. 3G illustrates the wearable device 100 with the light source 326and the first sensor 112 being located approximate the firstmuscular-walled tube 322 and the second sensor 114 being locatedapproximate the second muscular-walled tube 324, according to anembodiment. Some of the features in FIG. 3G are the same as or similarto some of the features in FIGS. 1-3F as noted by same and/or similarreference characters, unless expressly described otherwise. Furthermore,the elements and/or features described regarding FIG. 3G may be the sameas and/or similar to other similarly named elements and/or featuresdescribed and/or illustrated throughout this disclosure. In oneembodiment, the second sensor 114 may be located over the secondmuscular-walled tube 324. In one embodiment, the second sensor 114 mayinclude a miniaturized impedance sensor. In one embodiment, the secondmuscular-walled tube 324 may extend along a Y-axis of a first plane andthe miniaturized impedance sensor may extend parallel relative to thesecond muscular-walled tube 324 along a Y-axis of a second plane, suchthat the miniaturized impedance sensor may extend along a portion of thesecond muscular-walled tube 324. In another embodiment, the first sensor112 may be located at a first side of the first muscular-walled tube 322and the light source(s) 326 may be located on a second side of the firstmuscular-walled tube 322, such that the first sensor 112 and the lightsource(s) 326 may straddle each side of first muscular-walled tube 322.

FIG. 3H illustrates the wearable device 100 with the light source 326and the first sensor 112 being located approximate the secondmuscular-walled tube 324 and the second sensor 114 being locatedapproximate the first muscular-walled tube 322, according to anembodiment. Some of the features in FIG. 3H are the same as or similarto some of the features in FIGS. 1-3G as noted by same and/or similarreference characters, unless expressly described otherwise. Furthermore,the elements and/or features described regarding FIG. 3H may be the sameas and/or similar to other similarly named elements and/or featuresdescribed and/or illustrated throughout this disclosure. In oneembodiment, the second sensor 114 may be located over the firstmuscular-walled tube 322. In one embodiment, the second sensor 114 mayinclude a miniaturized impedance sensor. In one embodiment, the secondmuscular-walled tube 324 may extend along a Y-axis of a first plane andthe miniaturized impedance sensor may extend parallel relative to thefirst muscular-walled tube 322 along a Y-axis of a second plane, suchthat the miniaturized impedance sensor may extend along a portion of thesecond muscular-walled tube 324. In another embodiment, the first sensor112 may be located at a first side of the second muscular-walled tube324 and the light source(s) 326 may be located on a second side of thesecond muscular-walled tube 324, such that the first sensor 112 and thelight source(s) 326 may straddle each side of second muscular-walledtube 324.

FIGS. 3A-H illustrate the first sensor 112 and the light source 326straddling the muscular-walled tube 322 and/or the muscular-walled tube324. Such an arrangement may allow for precise detection by the firstsensor 112 of light scattered by the muscular-walled tube 322 and/or themuscular-walled tube 324. The arrangement may also reduce interferenceby and/or detection of light scattered by other structures within thepart of the body 320 to ensure a measurement taken by the first sensor112 corresponds to light scattered by the muscular-walled tube 322and/or the muscular-walled tube 324. A separation distance between thefirst sensor 112 and the light source 326 may also minimize an amount oflight scattered by a surface of the part of the body 320 such as skin onthe part of the body 320. In an embodiment, a curvature of the part ofthe body 320 may also allow for light from the light source 326 to passmore directly to the first sensor 112 as the light source 326 and thefirst sensor 112 straddle the muscular-walled tube 322 and/or themuscular-walled tube 324. In an embodiment, the first sensor 112 mayinclude a miniaturized spectrometer. The miniaturized spectrometer maycollimate light that passes into the miniaturized spectrometer, whichmay result in a decreased intensity of light striking a photosensorwithin the miniaturized spectrometer as tangential light rays areabsorbed, reflected, and/or otherwise deflected away from thephotosensor. However, as the light source 326 and the first sensor 112straddle the muscular-walled tube 322 and/or the muscular-walled tube324 and the curvature of the part of the body 320 aligns light emittedfrom the light source 326 more directly with the first sensor 112, anamount and therefore intensity of the light impinging on the firstsensor 112 may increase.

FIG. 3I illustrates a zoomed-in view of the wearable device 100,focusing in on the first sensor 112, the light source 326, and the firstmuscular-walled tube 322, according to an embodiment. Some of thefeatures in 3I are the same as or similar to some of the features inFIGS. 1-3H as noted by same reference characters, unless expresslydescribed otherwise. The light source 326 may be positioned over themuscular-walled tube. In an embodiment, a plurality of light sources 326may be positioned over the muscular-walled tube. The firstmuscular-walled tube 322 may extend along a Y-axis of a first plane andthe plurality of light sources 326 may extend over the muscular-walledtube 322 along the Y-axis. The first sensor 112 may be positionedapproximate the muscular-walled tube 322. In an embodiment, the firstsensor 112 may include a miniaturized spectrometer. The miniaturizedspectrometer may have a length along the Y-axis that is greater than alength of the miniaturized spectrometer along an X-axis of the firstplane. The arrangement of the light source 326 over the firstmuscular-walled tube 322 may allow for direct illumination of the firstmuscular-walled tube 322 by the light source 326. This may increase theamount of light scattered from the first muscular-walled tube 322 and/orreceived by the first sensor 112 relative to embodiments where the lightsource 326 is not positioned over the first muscular-walled tube 322.

FIG. 3J illustrates another zoomed-in view of the wearable device 100,focusing in on the first sensor 112, the light source 326, and the firstmuscular-walled tube 322, according to an embodiment. Some of thefeatures in 3J are the same as or similar to some of the features inFIGS. 1-3I as noted by same reference characters, unless expresslydescribed otherwise. The first sensor 112 may be positioned over themuscular-walled tube. The first muscular-walled tube 322 may extendalong a Y-axis of a first. In an embodiment, the first sensor 112 mayinclude a miniaturized spectrometer. The miniaturized spectrometer mayhave a length along the Y-axis that is greater than a length of theminiaturized spectrometer along an X-axis of the first plane. Theminiaturized spectrometer may accordingly be aligned over the firstmuscular-walled tube 322 parallel or roughly parallel to a length of thefirst muscular-walled tube 322 along the Y-axis. In an embodiment, thewearable device 100 includes a plurality of light sources 326. Theplurality of light sources 326 may be positioned approximate the firstmuscular-walled tube 322. The plurality of light sources 326 may bearranged in order along the Y-axis. The arrangement of the miniaturizedspectrometer over the first muscular-walled tube 322 may allow forgreater capture of light reflected by the first muscular-walled tube 322relative to embodiments where the miniaturized spectrometer is notpositioned over and/or aligned along with the first muscular-walled tube322.

In an embodiment, the wearable device 100 may include a flexible bandsuch as the band 106, the light source 326, an optical sensor, anoptical filter, and a collimator. The optical sensor, the opticalfilter, and/or the collimator may be integrated together to form aminiaturized spectrometer, such as the first sensor 112. The flexibleband may be configured to extend at least partially around a wrist ofthe user, such as the body part 320. The wrist may include a dermallayer along an underside of the wrist and the muscular-walled tube 322or 324 within the wrist adjacent to the dermal layer along the undersideof the wrist. T light source 326 may be embedded in the flexible bandand positioned in the flexible band to emit light into the wrist throughthe dermal layer along the underside of the wrist as the user wears theflexible band. The light source may be positioned in the flexible bandto be pressed into the wrist along a first side of the muscular-walledtube 322 or 324 as the user wears the flexible band. The optical sensormay be embedded in the flexible band and positioned in the flexible bandto be situated, as the user wears the flexible band, along a second sideof the muscular-walled tube 322 or 324 opposite the first side of themuscular-walled tube 322 or 324. The optical filter may be integratedinto the flexible band and may be configured to isolate a relevantconstituent wavelength of the light. The optical filter may bepositioned in the flexible band to filter the light emitted by the lightsource 326 before the light passes to the optical sensor. The collimatormay be integrated into the flexible band and positioned in the flexibleband to be situated, as the user wears the flexible band, along thesecond side of the muscular-walled tube 322 or 324. The collimator maybe positioned in the flexible band to collimate the light emitted by thelight source 326 before the light passes to the optical sensor. Theminiaturized spectrometer, with the optical sensor, the optical filter,and/or the collimator may be embedded in the flexible band to besituated along the second side of the muscular-walled tube opposite thelight source such that the light source 326 and the miniaturizedspectrometer straddle the muscular-walled tube 322 or 324.

In one example of the embodiment, the flexible band may include a firstend and a second end, and a clasp configured to join the first end tothe second end, or to join the first end or the second end to theflexible band. The light source 326 and the miniaturized spectrometermay be positioned in the flexible band adjacent to the clasp. Theflexible band may be configured to press the light source 326 or theminiaturized spectrometer against the wrist of the user as the userwears the flexible band. The flexible band may prevent the light source326 from being displaced from the first side of the muscular-walled tube322 or 324 as the user wears the flexible band. The flexible band mayprevent the miniaturized spectrometer from being displaced from thesecond side of the muscular-walled tube 322 or 324 as the user wears theflexible band.

In another example, the wearable device 100 may include user interface104 coupled to the flexible band and positioned on the flexible band tobe situated along a top side of the wrist opposite the underside of thewrist as the user wears the flexible band. The position of the userinterface 104 on the flexible band may correspond to a natural alignmentof the user interface 104 on the top side of the wrist for the user tointeract with the user interface 104 as the user wears the flexibleband. The light source 326 and the miniaturized spectrometer may bepositioned in the flexible band to straddle the muscular-walled tube 322or 324 as the user interface 104 is positioned in the natural alignmentas the user wears the flexible band. The muscular-walled tube 322 or 324may include an ulnar artery or a radial artery of the user. The naturalalignment of the user interface on the wrist may align the light sourceand the miniaturized spectrometer to straddle the ulnar artery or theradial artery as the user wears the flexible band. An axis may extendalong a width of the flexible band opposite the user interface 104. Thelight source 326 may be positioned in the flexible band at a first sideof the axis. The miniaturized spectrometer may be positioned in theflexible band at a second side of the axis.

In another example, the relevant constituent wavelength may an indicatorof an amount of glucose in blood flowing through the muscular-walledtube 322 or 324 as the user wears the flexible band.

In an example, the miniaturized spectrometer may be positioned in theflexible band to receive reflected light through the dermal layer as theuser wears the flexible band. The reflected light may be reflected bythe muscular-walled tube 322 or 324 or a material within themuscular-walled tube.

In an example, the light source 326 may be isolated from theminiaturized spectrometer. The flexible band may be configured inflexibility, size, or durability to press the light source 326 and theminiaturized spectrometer against the wrist as the user wears theflexible band. The flexible band and the dermal layer may create a firstoptical seal around the light source 326 as the user wears the flexibleband such that the light emitted from the light source is directed intothe wrist. The flexible band and the dermal layer may create a secondoptical seal around the miniaturized spectrometer as the user wears theflexible band such that the miniaturized spectrometer is isolated fromexternal light external to the wrist of the user.

In an example, the light source 326 may include a length and a width,and the flexible band may include a length and a width. The light source326 may be oriented in the flexible band such that the light source 326length is perpendicular to the band 106 length. The orientation of thelight source 326 may align the light source 326 approximately parallelto the muscular-walled tube 322 or 324 as the user wears the flexibleband to emit light through a plurality of positions along a length ofthe muscular-walled tube 322 or 324. Similarly, the miniaturizedspectrometer may include a length and a width. The miniaturizedspectrometer may be oriented in the flexible band such that thespectrometer length is perpendicular to the band 106 length. Theorientation of the miniaturized spectrometer may align the miniaturizedspectrometer approximately parallel to the muscular-walled tube 322 or324 as the user wears the flexible band to receive the light emitted bythe light source 326 through a plurality of positions along a length ofthe muscular-walled tube 22 or 324.

In an embodiment, the wearable device 100 may include the band 106, thelight source 326, the optical sensor, the optical filter, and thecollimator. The optical sensor, the optical filter, and/or thecollimator may be integrated together to form a miniaturizedspectrometer such as the first sensor 112. The band 106 may beconfigured to extend at least partially around the body part 320 of theuser. The body part 320 may include a dermal layer around the body part320 and the muscular-walled tube 322 or 324 within the body part 320adjacent to the dermal layer. The light source 326 may be integratedinto the band 106. The light source 326 may be positioned in the band106 to emit light into the body part 320 through the dermal layer as theuser wears the band 106. The light source 326 may be positioned in theband 106 to be pressed against the dermal layer over the muscular-walledtube 322 or 324 as the user wears the band 106 such that the dermallayer is situated directly between the muscular-walled tube 322 or 324and the light source 106. The light source 326 may be positioned along afirst side of the muscular-walled tube 322 or 324 as the user wears theband 106. The optical filter may be integrated into the band 106. Theoptical filter may be configured to isolate a relevant constituentwavelength of the light. The optical filter may be positioned in theband to filter the light emitted by the light source 326 before thelight passes to the optical sensor. The collimator may be positionedrelative to the optical sensor to collimate the light emitted by thelight source 326 before the light passes to the optical sensor. Theminiaturized spectrometer may be integrated into the band 106 to besituated along a first side of the muscular-walled tube 322 or 324adjacent to the light source. 326

In an example of the embodiment, the light source 326 may include alength and a width, and the band 106 may include a length and a width.The light source 326 may be oriented in the band 106 such that the lightsource 326 length is perpendicular to the band 106 length. Theorientation of the light source 326 may align the light source 326approximately parallel to the muscular-walled tube 322 or 324 as theuser wears the band 106 to emit light along a length of themuscular-walled tube 322 or 324.

In another example, the band 106 may form a shape, the shape beingapproximately circular or approximately elliptical. The light source 326may be positioned in the band 106 along a same side of the band 106 asthe miniaturized spectrometer. The wearable device 100 may include theuser interface 104 coupled to the band 106. The user interface 104 maybe positioned on the band 106 along an opposite side of the band 106from the light source 326 or the miniaturized spectrometer when the userwears the band 106. The light source 326 and the miniaturizedspectrometer may face inwards into the band 106 and the user interface104 may face outwards from the band 106.

In one embodiment, the wearable device 100 may include the band 106, thelight source 326, the optical sensor, the optical filter, and thecollimator. The optical sensor, the optical filter, and/or thecollimator may be integrated together to form the miniaturizedspectrometer. The band 106 may be configured to extend at leastpartially around the body part 320 of the user. The body part 320 mayinclude a dermal layer around the body part 320 and a subdermal featurewithin the body part adjacent to the dermal layer. The light source 326may be integrated into the band 106. The light source 326 may bepositioned in the band 106 to emit light into the body part through thedermal layer as the user wears the band 106. The optical filter may beintegrated into the band. The optical filter may be configured toisolate a relevant constituent wavelength of the light. The opticalfilter may be positioned in the band 106 to filter the light emitted bythe light source 326 before the light passes to the optical sensor. Thecollimator may be positioned relative to the optical sensor to collimatethe light emitted by the light source 326 before the light passes to theoptical sensor. The miniaturized spectrometer may be positioned in theband 106 to be situated adjacent to the dermal layer over the subdermalfeature as the user wears the band 106 such that the dermal layer issituated directly between the subdermal feature and the miniaturizedspectrometer as the user wears the band 106.

In an example of the embodiment, the light source 326 may be positionedin the band 106 adjacent to the miniaturized spectrometer along a lengthof the band 106 such that, as the user wears the band 106, the lightsource 326 is positioned along the dermal layer offset from thesubdermal feature. The light source 326 may be positioned in the band106 adjacent to the miniaturized spectrometer along a width of the band106 such that, as the user wears the band 106, the light source 326 ispositioned along the dermal layer over the subdermal feature. The dermallayer may be situated directly between the light source 326 and thesubdermal feature.

In another example, the wearable device 100 may include the userinterface 104 coupled to the band 106 and an axis extending along awidth of the band 106 directly opposite the user interface 104. Thelight source 326 and the miniaturized spectrometer may be off-centeredin the band 106 relative to the user interface 104 such that the lightsource 326 and the miniaturized spectrometer may be positioned in theband 106 along a first side of the axis closer to a first side of theuser interface 104 along the band 106 than to a second side of the userinterface 104 along the band 106. The light source 326 and theminiaturized spectrometer may be aligned in the band 106 approximatelyparallel to each other.

In another embodiment, the wearable device 100 may include a flexibleband such as the band 106, the user interface 104, the light source 326,a miniaturized spectrometer such as the first sensor 112, an impedancesensor such as the second sensor 114, and the processing device 102. Theflexible band may be designed to flex into a curvilinear shape, and mayinclude a shape, size, and flexibility designed for attaching theflexible band to a wrist of the user, such as the body part 320. Thewrist may include a dermal layer along an underside of the wrist and themuscular-walled tube 322 or 324 within the wrist adjacent to the dermallayer along the underside of the wrist. The user interface 104 may becoupled to the flexible band and positioned on the flexible band to besituated, as the user wears the flexible band, adjacent to a top side ofthe wrist opposite the underside of the wrist. The light source 326 maybe embedded in the flexible band. The light source 326 may be positionedin the flexible band to emit light into the wrist through the dermallayer along the underside of the wrist as the user wears the flexibleband. The miniaturized spectrometer may be embedded in the flexible bandand positioned in the flexible band to press against the underside ofthe wrist as the user wears the flexible band to receive the lightthrough the dermal layer. The miniaturized spectrometer may include anoptical filter, a collimator, and/or an optical sensor. The opticalfilter may be configured to isolate a relevant constituent wavelength ofthe light. The relevant constituent wavelength may indicate a feature ofthe muscular-walled tube 322 or 324 or of blood flowing through themuscular-walled tube 322 or 324. The collimator may be configured tocollimate the light received by the miniaturized spectrometer. Theoptical sensor may be configured to detect an intensity of the relevantconstituent wavelength. The impedance sensor may be embedded in theflexible band and positioned in the flexible band to be situated, as theuser wears the flexible band, against the underside of the wrist. Theimpedance sensor may include two or more rows of microelectrodes. Theprocessing device 102 may be coupled to the flexible band andcommunicatively coupled to the optical sensor and the impedance sensor.The miniaturized spectrometer and the impedance sensor may be positionedin the flexible band to simultaneously measure, as the user wears theflexible band, the feature of the muscular-walled tube 322 or 324 or ofthe blood flowing through the muscular-walled tube 322 or 324.

In one example of the embodiment, the impedance sensor may be positionedin the flexible band to be aligned approximately radially with themuscular-walled tube 322 or 324 as the user wears the flexible band. Thelight source 326 and the miniaturized spectrometer may be positioned inthe flexible band to straddle the impedance sensor, the light source 326positioned along a first side of the impedance sensor, and theminiaturized spectrometer positioned along a second side of theimpedance sensor opposite the first side of the impedance sensor. Theimpedance sensor may be positioned in the flexible band such that thetwo or more rows of microelectrodes are aligned in the flexible band tobe approximately parallel to the muscular-walled tube 322 or 324 orapproximately perpendicular to the muscular-walled tube 322 or 324 asthe user wears the flexible band.

In another example, the light source 326 may be positioned in theflexible band to be situated along a first side of the muscular-walledtube 322 or 324 against the dermal layer as the user wears the flexibleband. The miniaturized spectrometer may be positioned in the flexibleband to be situated along a second side of the muscular-walled tubeagainst the dermal layer as the user wears the flexible band. The lightsource 326 and the miniaturized spectrometer may be positioned in theflexible band to straddle the muscular-walled tube 322 or 324 as theuser wears the flexible band. The light source 326 may be positionedalong a first side of the muscular-walled tube 322 or 324, and theminiaturized spectrometer may be positioned along a second side of themuscular-walled tube 322 or 324 opposite the first side of themuscular-walled tube. The impedance sensor may be positioned in theflexible band to be aligned approximately radially with a secondmuscular-walled tube 322 or 324 as the user wears the flexible band. Thesecond muscular-walled tube 322 or 324 may be adjacent to the dermallayer along the underside of the wrist.

In another example, the processing device 102 may be configured tomeasure blood glucose simultaneously by the miniaturized spectrometerand the impedance sensor. The impedance sensor, the miniaturizedspectrometer, and/or the light source 326 may be positioned in theflexible band adjacent to each other. The impedance sensor and theminiaturized spectrometer or the light source 326 are positioned in theflexible band to be aligned approximately radially with themuscular-walled tube 322 or 324 as the user wears the flexible band.

In another example, the processing device 102 may be configured tomeasure, by the impedance sensor, a hydration condition of the user. Theprocessing device 102 may be configured to measure, by the miniaturizedspectrometer, a blood glucose level of the user. The processing device102 may be configured to adjust a measurement of the blood glucose levelof the user based on the hydration condition of the user, where a changein the hydration condition of the user skews the measurement of theblood glucose level.

In another example, the miniaturized spectrometer or the light source326 may be positioned in the flexible band to be aligned approximatelyradially with the muscular-walled tube 322 or 324 as the user wears theflexible band. The impedance sensor may be positioned in the flexibleband to be aligned approximately radially with the muscular-walled tube322 or 324 as the user wears the flexible band.

In an embodiment, the wearable device 100 may include the band 106, thelight source 326, the miniaturized spectrometer, and the impedancesensor. The band 106 may be configured to extend at least partiallyaround the body part 320 of the user, the body part 320 including adermal layer and a subdermal feature within body part 320. The lightsource 326 may be integrated into the band 106, where the light source326 is configured in the band to emit light into the body part 320through the dermal layer. The miniaturized spectrometer may beintegrated into the band 106 and positioned in the band 106 to pressagainst the body part 320 as the user wears the band 106 to receive thelight through the dermal layer. The miniaturized spectrometer mayinclude an optical filter, a collimator, and an optical sensor. Theoptical filter may be configured to isolate a relevant constituentwavelength of the light, the relevant constituent wavelength indicatinga condition or a constituent of the body part 320, the dermal layer, orthe subdermal feature. The collimator may be configured to collimate thelight received by the miniaturized spectrometer. The optical sensor maybe configured to detect an intensity of the relevant constituentwavelength. The impedance sensor may be integrated into the band 106 andconfigured to be positioned, as the user wears the band, against a sameside of the body part 320 as the miniaturized spectrometer. Theminiaturized spectrometer may be configured in the band 106 to bepositioned along a same side of the body part as the impedance sensorwhen the user wears the band 106.

In one example of the embodiment, the wearable device 100 may includethe processing device 102. The processing device 102 may be configuredto take, by the optical sensor, an optical measurement, and take, by theimpedance sensor, an impedance measurement simultaneously with theoptical measurement. The processing device 102 may be configured to:correlate the impedance measurement and the optical measurement; anddetermine glucose measurement of the body part 320, the dermal layer, orthe subdermal structure based on the correlation. The opticalmeasurement may indicate a change in the glucose measurement, where thechange in the glucose measurement is a combination of a change inglucose and a change in hydration in the body part 320, the dermallayer, or the subdermal structure. The impedance measurement mayindicate the change in the hydration in the body part 320, the dermallayer, or the subdermal structure. The processing device 102 may beconfigured to filter out the change in the hydration based on theimpedance measurement from the glucose measurement to generate a glucoseindicator.

In another example, the miniaturized spectrometer or the impedancesensor may positioned in the band 106 to be situated, as the user wearsthe band 106, against a region of the dermal layer directly adjacent tothe subdermal structure. The body part 320 may be approximatelycircular, approximately oval-shaped, or approximately elliptical. Thebody part 320 may include a radius, the subdermal structure beingaligned in the body part approximately along the radius. Theminiaturized spectrometer or the impedance sensor may be positioned inthe band 106 to be aligned, as the user wears the band, radially withthe subdermal structure.

In an embodiment, a method of using the wearable device 100 to take ameasurement may include placing the wearable device 100 at leastpartially around the body part 320 of the user, where the wearabledevice 100 may include structure or programming to take simultaneousmeasurements of a feature of the body part 320 with two different typesof sensors. The wearable device 100 may include the band 106, the lightsource 326, the miniaturized spectrometer, the impedance sensor, and theprocessing device 102. The band 106 may be shaped to extend at leastpartially around the body part 320 of the user. The body part 320 mayinclude a dermal layer, a subdermal structure within body part 320, afirst side, and a second side facing a different direction than thefirst side. The light source 326 may be integrated into the band 320.The light source 326 may be configured in the band 106 to emit lightinto the body part 320 through the dermal layer. The miniaturizedspectrometer may be integrated into the band 106 and positioned in theband 106 to press against the body part 320 as the user wears the band106 to receive the light through the dermal layer. The miniaturizedspectrometer may include the optical filter, the collimator, and theoptical sensor. The optical filter may be configured to isolate arelevant constituent wavelength of the light, the relevant constituentwavelength indicating a condition or a constituent of the body part 320,the dermal layer, or the subdermal feature. The collimator may beconfigured to collimate the light received by the miniaturizedspectrometer. The optical sensor may be configured to detect anintensity of the relevant constituent wavelength. The impedance sensormay be integrated into the band 106 and positioned in the band 106 to besituated along a same side of the body part 320 as the miniaturizedspectrometer as the user wears the band 106. The same side may includeeither the first side of the body part 320 or the second side of thebody part 320. The processing device 102 may be configured to takesimultaneous measurements with the miniaturized spectrometer and theimpedance sensor, the processing device communicatively coupled to theimpedance sensor and the optical sensor. The method may include:emitting, by the light source, the light through the body part;detecting, by the optical sensor, the relevant constituent wavelength;measuring an impedance of the body part by the impedance sensorsimultaneously with the light source emitting the light and the opticalsensor detecting the relevant constituent wavelength; and communicatingto the processing device an impedance measurement from the impedancesensor and an optical measurement from the optical sensor.

In one example of the embodiment, the method may include comparing theimpedance measurement and the optical measurement to determine afeature, a condition, or a constituent of the subdermal structure. Themethod may include determining, based on the impedance measurement orthe optical measurement, an alignment of the wearable device on the bodypart relative to the subdermal structure. The method may include:determining, by the processing device, a first condition of the bodypart based on the impedance measurement; determining, by the processingdevice 102, a second condition of the body part based on the opticalmeasurement; comparing, by the processing device 102 the first conditionof the body part with the second condition of the body part; anddetermining whether the first condition and the second condition areindependent conditions or dependent conditions based on the comparison.The method may include aligning the wearable device on the body part 320such that the impedance sensor or the miniaturized spectrometer arealigned radially with the subdermal structure on the body part 320. Thebody part may be approximately circular, approximately oval-shaped, orapproximately elliptical, and the body part 320 may have a radiusextending from a center of the body part outward towards the dermallayer and perpendicular with the dermal layer.

FIG. 4 illustrates a view of the wearable device 100 around a body part400 of the user with the light source 326 emitting light 402 through thebody part 400 to the first sensor 112, according to an embodiment. Someof the features in FIG. 4 are the same as or similar to some of thefeatures in FIGS. 1-3H as noted by same reference numbers, unlessexpressly described otherwise. The body part 400 may include a dermallayer 404, a subdermal layer 406, and a muscular-walled tube 408. In anembodiment, the body part 400 may include a wrist of the user. Themuscular-walled tube 408 may include a vein or an artery of the user.The wearable device 100 may include the band 106 which may wrap aroundthe body part 400. The light source 112 may be positioned within theband 106 to face the body part 400 when the band 106 is wrapped aroundthe body part 400. The first sensor 112 may include a miniaturizedspectrometer. The first sensor 112 may be disposed within the band 106to face the body part 400 as the band 106 is wrapped around the bodypart 400.

In an embodiment, the light source 326 may be at least partially exposedfrom the band 106. For example, an illuminating portion of the lightsource may be exposed from the band 106 such that the illuminatingportion of the light source 326 protrudes from the band 106 or is setwithin the band 106, forming a discontinuity in an inside surface 106 aof the band 106. In another example, the illuminating portion of thelight source 326 may be flush with the inside surface 106 a of the band106 to form a continuous surface with the inside surface 106 a. In anembodiment, the first sensor 112 may be at least partially exposed fromthe band 106. For example, a surface 112 a of the first sensor 112 maybe flush with the inside surface 106 a of the band 106 such that thesurface 112 a of the first sensor 112 and the inside surface 106 a ofthe band 106 form a continuous surface. In another example, the firstsensor 112 may protrude from the band 106. The band may encompass aportion of the first sensor 112, and a portion of the first sensor 112may extend from the band 106. In yet another example, the first sensor112 may be set within the band 106, forming a cavity in the band 106over the first sensor 112. The cavity in the band 106 may form adiscontinuity in the inside surface 106 a of the band 106.

In an embodiment, the light source 326 may emit the light 402omnidirectionally or partially omnidirectionally. For example, the lightsource 326 may emit the light 402 omnidirectionally beyond the insidesurface 106 a of the band 106. In another embodiment, the light may bechanneled and/or directed in a direction and/or within a range ofdirections corresponding to polar and/or azimuthal ranges. For example,the light 402 may be emitted in a 360 degree polar range and a 180degree azimuthal range. The polar range may vary from 1 degree to 360degrees. The azimuthal range may vary from 1 degree to 300 degrees. Inan embodiment, the light 402 may be a ray of unidirectional light. Thelight 402 as initially emitted from the light source 326 may include aspectrum of wavelengths. The light 402 may be monochromatic or polychromatic. The light 402 may be emitted from the light source 326 at aspecific, selected, and/or known intensity level, where the intensitylevel may be known to a processing device disposed in the housing 118and electrically coupled to the light source 326 and/or the first sensor112. For example, the intensity level of the light 402 may be stored intransitory and/or non-transitory memory and/or into the processingdevice (such as in a cache of the processing device), or the intensitylevel of the light 402 may be measured and communicated to theprocessing device when the light 402 is emitted from the light source326.

The light 402 may be reflected as it passes through the body part 400 sothat it strikes the first sensor 112. As described earlier, the lightsource 326 may emit the light 402 omnidirectionally. The light 402 mayinclude light rays 402 a-d. The light rays 402 a-d may follow differentpaths through the body part 400, and in an embodiment the light rays 402a-d may each be reflected towards the first sensor 112. As the lightrays 402 a-d are emitted from the light source 326, each light ray 402a-d may have a same and/or similar light profile as each other light ray402 a-d. The light profile may include the wavelength of the light 402,the intensity of the light 402, and/or the phase of the light 402. Asthe light rays 402 a-d pass through the body part 400, the light profilefor each light ray 402 a-d may change differently from each other lightray 402 a-d. Accordingly, each light ray 402 a-d may have a differentlight profile from each other light ray 402 a-d as it impinges on (i.e.strikes) the first sensor.

As the light 402 travels through the body part 400, the light 402 mayreflect off a variety of tissues and/or other constituents within thebody part 400. The light 402 may follow a non-linear path through thebody part 400 from the light source 326 to the first sensor 112. In anembodiment, the path the light 402 follows may go through the dermallayer 404, the subdermal layer 406, and/or the muscular-walled tube 408.As the light 402 passes through the body part 400, constituents and/ortissues of the body part 400 may absorb and/or reflect variouswavelengths of the light 402. For example, the muscular-walled tube 408may include a vein or an artery. The vein or the artery may carry bloodwithin the vein or artery. The blood may include various constituents,including red blood cells, white blood cells, water, platelets, glucose,mineral ions, hormones, proteins, and so forth. The various constituentsof the blood may strongly absorb, transmit, and/or reflect light indifferent ways. For example, red blood cells may strongly absorbwavelengths ranging from 400 nanometers (nm) to 450 nm. Blood glucosemay strongly reflect and/or transmit wavelengths ranging from 725 nm to775 nm, from 1050 nm to 1100 nm, and/or from 1550 nm to 1700 nm.

Each wavelength may reflect a blend of constituents. Each constituent ofblood may have a unique absorbance corresponding to a single wavelength.A resulting intensity of a wavelength passing through the vein or theartery may be the result of the combined effects of each of theconstituent's absorbance coefficients and the respective concentrationsof the constituents. The Beer-Lambert Law may be one way of concretelyquantifying this effect. Quantifying the relative amount of the variousblood constituents may be accomplished by determining relativeintensities of several wavelengths and determining which combination ofeach of the constituents would give the net result. The quantificationmay be accomplished by a multivariate regression analysis and/or othermachine learning algorithm based on an iterative optimization problem toreduce error from a training set.

The first sensor 112 may collimate the light rays 402 a-d such that thelight 402 striking the first sensor surface 112 a at a roughly normalangle may pass into the first sensor 112. For example, light strikingthe first sensor surface 112 a at an angle ranging from 60 degrees to 90degrees, from 70 degrees to 90 degrees, from 75 degrees to 90 degrees,from 80 degrees to 90 degrees, and/or from 85 degrees to 90 degrees maypass into the first sensor 112. The first sensor 112 may filter thelight rays 402 a-d and may detect one or more features of the lightprofile of to each light ray 402 a-d. The detected features may becommunicated to the processing device. The processing device may performone or more of various calculations and/or functions using and/or basedon a comparison and/or analysis of the light profile of the light 402 asemitted from the light source 326 and light profiles of the light rays402 a-d detected by the first sensor 112.

In one embodiment, the wearable device 100 may include a flexible bandsuch as the band 106, the user interface 104, the processing device 102,the light source 326, the miniaturized spectrometer such as the firstsensor 112, and/or the electrical trace 108. The flexible band may beconfigured to extend at least partially around a wrist of a user, thewrist including the dermal layer 404 and the muscular-walled tube 408within the wrist adjacent to a section of the dermal layer 404 along anunderside of the wrist. The user interface 104 may be coupled to theflexible band. The processing device 102 may be coupled the flexibleband. The light source 326 may be embedded in the flexible band. Thelight source 326 may be configured to press against the dermal layer 404by the flexible band as the user wears the flexible band and emit lightinto the underside of the wrist as the user wears the flexible band. Theminiaturized spectrometer may be integrated into the flexible band andpositioned in the flexible band to: press against the dermal layer 404along the underside of the wrist as the user wears the flexible band;and receive the light from the light source 326 through the underside ofthe wrist or the muscular-walled tube as the user wears the flexibleband. The miniaturized spectrometer may include a collimator, an opticalfilter, and an optical sensor. The collimator may include a microtube,the microtube including a wall defining a through-channel, and the wallincluding a carbon nanotube forest. The carbon nanotube forest mayinclude a bundle of carbon nanotubes aligned approximately parallel witheach other. The optical filter may be configured to have a passbandcorresponding to a wavelength of light providing an indication of acondition or constituent of the wrist, the dermal layer 404, or themuscular-walled tube 408. The optical sensor or processing device 102may be configured to: identify the wavelength of light; and measure anintensity of the wavelength of light. The collimator, the opticalfilter, or the optical sensor may be stacked together. The electricaltrace 108 may be integrated into the flexible band and electricallyinterconnect the processing device 102, the user interface 104, thelight source 326, or the optical sensor.

In an example of the embodiment, a borosilicate glass may be stackedwith the collimator, the optical filter, or the optical sensor, wherethe borosilicate glass is aligned flush with the inside surface 106 a ofthe flexible band, the inside surface 106 a designed to face the wristof the user as the user wears the flexible band.

In one example, identifying the wavelength may include correlating aposition on the optical sensor where the light strikes the opticalsensor with a segment of the optical filter aligned with the position onthe optical sensor. The segment of the optical filter may include apassband for the wavelength.

In another example, the collimator may be positioned in the stack topress against the wrist as the user wears the flexible band, where thecollimator is positioned, as the user wears the flexible band, tocollimate the light to enable the light to strike a portion of theoptical sensor corresponding to a portion of the filter through whichthe light passed. Or, the filter may be positioned in the stack to pressagainst the wrist as the user wears the flexible band to enable filteredlight to be collimated and passed to the portion of the optical sensorcorresponding to the portion of the filter through which the lightpassed.

In an example, the processing device 102 may be configured to determinea constituent of the muscular-walled tube 408 based on the intensity ofthe wavelength.

In an example, the inward-facing surface 112 a of the miniaturizedspectrometer may be flush with the inside surface 106 a of the flexibleband. The inward-facing surface 112 a of the miniaturized spectrometermay be positioned in the flexible band to be pressed against the wristof the user as the user wears the flexible band to prevent outside lightfrom outside the wrist from entering the miniaturized spectrometer orreaching the optical sensor as the user wears the flexible band. Theinward-facing surface 112 a may be configured to receive the light intothe miniaturized spectrometer through the wrist as the user wears theflexible band. The inside surface 106 a of the flexible band may facethe wrist as the user wears the flexible band.

In another example, the light source 326 and the miniaturizedspectrometer may be positioned in the flexible band relative to eachother to prevent light noise from being detected by the miniaturizedspectrometer, where the light noise includes external light entering theminiaturized spectrometer from outside the wrist. The light source 326and the miniaturized spectrometer are spaced from each other in theflexible band to prevent light emitted by the light source travelingoutside the wrist from being detected by the miniaturized spectrometeras the user wears the flexible band. The light source 326 may berecessed in the flexible band to prevent light emitted by the lightsource from traveling outside the wrist as the user wears the flexibleband.

In another example, the user interface 104 may be coupled to the band106 to be positioned on a top side of the wrist opposite the lightsource or the miniaturized spectrometer as the user wears the flexibleband. The user interface may be coupled to the flexible band in aposition to orient the user to align the light source 326 or theminiaturized spectrometer with the muscular-walled tube 408 as the userwears the flexible band.

In an embodiment, the wearable device 100 may include the band 106 andthe miniaturized spectrometer. The band 106 may be configured to extendat least partially around the body part 400 of a user, the body part 400including the dermal layer 404 and a subdermal feature within the bodypart 400. The light source 326 may be embedded in the band 106, wherethe light source 326 may be configured to emit light into the body part400 as the user wears the band 106. The miniaturized spectrometer may beintegrated into the band, and may include a collimator, an opticalfilter, and an optical sensor. The collimator may collimate the light,and may include a plurality of microtubes, where the microtubes includecarbon nanotube walls defining a plurality of through-channels. Theoptical filter may filter the light and may be configured to have aplurality of passbands corresponding to constituent wavelengths of thelight. The optical sensor may be configured to detect the intensities ofthe constituent wavelengths and communicate the intensities to theprocessing device. The miniaturized spectrometer may be configured to:collimate the light; filter the light into the relevant constituentwavelengths, where the relevant constituent wavelengths are reflected byor transmitted through the body part 400, the dermal layer 404, or thesubdermal feature as the user wears the band; and detect the intensitiesof the constituent wavelengths.

In one example of the embodiment, the light source 326 may include alight-emitting portion flush with the inside surface 106 a of the band106. The inside surface 106 a of the band 106 may face the body part 400as the user wears the band. The receiving surface 112 a of theminiaturized spectrometer may be flush with the inside surface 106 a ofthe band 106. The receiving surface 112 s may be configured to receivethe light into the miniaturized spectrometer through the body part 400as the user wears the band 106. The inside surface 106 a of the band mayface the body part 400 as the user wears the band 106.

In another example, the wearable device 100 may include the userinterface 104, where the user interface 104 may be coupled to the band106 to be adjacent to a side of the body part 400 opposite the lightsource 326 or the miniaturized spectrometer as the user wears the band106. The wearable device 100 may include the processing device 102configured to identify, as the user wears the band 106, a quantity of aconstituent of the subdermal feature based on the intensities of theconstituent wavelengths.

In one example, the light source 326 and the miniaturized spectrometermay be spaced from each other in the band 106 to prevent light emittedby the light source 326 and traveling outside the body part 400 frombeing detected by the miniaturized spectrometer as the user wears theband 106. The band 106 may be configured to press the light source 326and the miniaturized spectrometer into the wrist, and/or the lightsource 326 and the miniaturized spectrometer may be recessed within theband 106.

In one embodiment, the wearable device 100 may include the band 106, thelight source 326, the collimator, and/or the optical sensor, where thecollimator, optical sensor, or the optical filter are arranged togetherto form a stack embedded in the band. The band 106 may be configured toextend at least partially around the body part 400 of the user, the bodypart 400 including an internal feature within the body part 400. Thelight source 326 may be embedded in the band, where the light source 326may be configured to emit light into the body part 400 as the user wearsthe band 106. The collimator and the optical sensor may be stackedtogether. The optical sensor may be positioned in the stack to detectlight passing through the body part 400 as the user wears the band. Thecollimator may be positioned in the stack to be between the opticalsensor and the body part 400 as the user wears the band 106. The opticalfilter may be positioned in the band 106 adjacent to the light source326. The optical filter may be positioned in the band 106 to be betweenthe light source 326 and the body part 400 as the user wears the band106.

In one example of the embodiment, the light source 326 may include alight-emitting portion flush with the inside surface 106 a of the band106. The inside surface 106 a of the band may face the body part 400 asthe user wears the band 400. The receiving surface 112 a of theminiaturized spectrometer may be flush with the inside surface 106 a ofthe band 106. The receiving surface 112 a may be configured to receivethe light into the miniaturized spectrometer through the body part 400as the user wears the band 106. The inside surface 106 a of the band 106may face the body part 400 as the user wears the band 106.

FIG. 5A illustrates a side perspective exploded view of the first sensor112, according to an embodiment. Some of the features in FIG. 5A are thesame as or similar to some of the features in FIGS. 1-4 as noted by samereference numbers, unless expressly described otherwise. In oneembodiment, the first sensor 112 may include a miniaturizedspectrometer. The first sensor 112 may include a filter 528, acollimator 530, and an optical sensor 532. In one embodiment, the filter528 may be an optical filter, such as a variable filter, a linearvariable filter, an absorptive filter, a dichroic filter, amonochromatic filter, an infrared filter, an ultraviolet filter, aneutral density filter, a longpass filter, a band-pass filter, ashortpass filter, a guided-mode resonance filter, a metal mesh filter, apolarizer filter, an arc welding filter, a wedge filter, and so forth.In another embodiment, the filter may be a Fabry-Perot Etalon filter. Inyet another embodiment, the filter 528 may include colored glass.

In an embodiment, the filter 528 may allow light of a particularwavelength and/or range of wavelengths to pass through the filter 528while attenuating other wavelengths of light. The filter 528 mayaccomplish this by attenuating a significantly higher portion of theintensity of other wavelengths. For example, the filter 528 mayattenuate 90% of the intensity of wavelengths up to 550 nm, the filter528 may attenuate 100% of the intensity of wavelengths equal to orgreater than 750 nm, and the filter 528 may attenuate the intensity ofwavelengths between 550 nm and 750 nm according to a curve with a peakat 700 nm.

In an embodiment, the filter 528 may allow a user to select whichwavelengths of light may be detected by the optical sensor 532. Thefilter 528 may include a variable filter such as a linear variablefilter which may have a spatially variable response to impinging light.The filter 528 may include a first region 528 a corresponding to a firstrange of wavelength, a second region 528 b corresponding to a secondrange of wavelengths, a third region 528 c corresponding to a thirdrange of wavelengths, a fourth region 528 d corresponding to a fourthrange of wavelengths, a fifth region 528 e corresponding to a fifthrange of wavelengths, a sixth region 528 f corresponding to a sixthrange of wavelengths, and a seventh region 528 g corresponding to aseventh range of wavelengths. Each corresponding range of wavelengthsmay include a wavelength and/or range of wavelengths that, at a positionwithin the corresponding region, are passed through at a maximumintensity greater than an intensity for which any other wavelengthpasses through the filter 528 at the same position.

A linear variable filter may allow for selecting which wavelengthsstrike the optical sensor 532 at a specific position on the opticalsensor 532. This may allow a processing device to, in turn, distinguishthe relative intensities of wavelengths reflected from a tissue todetermine which wavelengths are most strongly reflected from the tissuerelative to an initial intensity of those wavelengths as emitted from alight source. The processing device may determine, based on thereflected wavelengths, one or more parameters, constituents, and/orconditions of the tissue. For example, light having a first wavelengthmay strike a first region of the optical sensor 532 corresponding to thefirst region 528 a of the filter 528. The first wavelength maycorrespond to a constituent of a user's blood. The optical sensor 532may communicate the intensity of the first wavelength to the processingdevice. The processing device may process the first wavelength based onan initial intensity of the wavelength, an expected attenuation of thewavelength, and/or other attenuation factors to determine an amount ofthe constituent in the user's blood. Different constituents of theuser's blood may correspond different wavelengths and/or differenttransmitted intensities of the same wavelengths. The filter 528 may passthose wavelengths corresponding to the blood constituents to differentpositions on the optical sensor 532. The optical sensor 532 may pass theintensities of the corresponding wavelengths to the processing device,and the processing device may determine an amount of each bloodconstituent based on the intensity of each corresponding wavelength.

In an embodiment, in the first region 528 a, wavelengths ranging from400 nm to 450 nm may pass through the filter 528 with an average of upto 50% of an impinging intensity for light impinging on the first region528 a of the filter 528. In the first region 528 a, wavelengths lessthan 400 nm and greater than 450 nm may be attenuated to 0% of theimpinging intensity. In the second region 528 b, wavelengths rangingfrom 450 nm to 500 nm may pass through the filter 528 with an average ofup to 50% of the impinging intensity, whereas wavelengths less than 450nm and greater than 500 nm may be attenuated to 0% of the impingingintensity. The pattern may continue for each of the third region 528 c,the fourth region 528 d, the fifth region 528 e, the sixth region 528 f,and/or the seventh region 528 g. In an embodiment, a position withineach region along a length of the filter 528 may correspond to a uniquewavelength having the maximum pass-through intensity. For example,within the first region 528 a, light having a wavelength of 400 nm maypass through the filter 528 with 50% of the impinging intensity at afirst position, whereas light having a wavelength of 405 nm may beattenuated to 0% of the impinging intensity at the first position. At asecond position within the first region 528 a, the 405 nm light may passthrough the filter with 50% of the impinging intensity, whereas the 400nm light may be attenuated to 0% of the impinging intensity at thesecond position.

In an embodiment, the linear variable filter may include a gradientalong which wavelengths filtered by the filter 528 may vary. Thegradient may contribute to an increased width of a transmission curve ofthe filter 528. The gradient may, for example, be 0.035 nm per micron.One or more of the microtubes of the collimator 530 may have a width ofa through-channel of the at least one microtube that may be 100 microns.Accordingly, the filter 528 may allow a 35 nm range of wavelengthspassing through the collimator to also pass through the filter 528. Afull width half maximum (FWHM) passband of the filter 528 correspondingto the one or more microtubes may range from 1 percent to 2 percent of awavelength of peak transmission. Depending on the wavelength of peaktransmission, a passband of the filter 528 corresponding to the one ormore microtubes may have an apparent FWHM passband that is 1.5 times to3 times wider than an actual FWHM passband of the filter 528 at alocation of the at least one microtube. Amplification of the apparentFWHM passband may be minimized by reducing a width of the microtube orby quantizing within the microtube in software.

In an embodiment, the linear variable filter may have a gradient that islarge compared to the width of the microtube such that a singlemicrotube may correspond to a relatively wide passband. Quantizingwithin the microtube may include, in one embodiment, treating lightentering the microtube in software as having the same center wavelengthand reporting the intensity of the center wavelength as a combinedresult of the intensities of all the wavelengths corresponding to themicrotube. In another embodiment, quantizing within the microtube mayinclude having an optical sensor 532 with a photodiode array. Theelements, i.e. pixels, of the array may be sized relative to themicrotube such that a plurality of the elements may fit within themicrotube. The elements may be assigned different wavelengthscorresponding to the elements' positions relative to the filter and/orthe microtube.

In one embodiment, a physiological constituent of interest may beglucose. The glucose may be blood glucose. The blood glucose may have aunique spectral profile for wavelengths ranging from 700 nm to 2500 nm,which may be referred to as a general band for glucose. The spectralprofile may be characterized by each wavelength within the general bandfor glucose having a transmission percentage. The spectral profile maybe a combination of the transmission percentages for each wavelengthwithin the general band for glucose. In an embodiment, narrower bandswithin the general band for glucose may be identified for which theblood glucose may have unique spectral profiles. The narrower bands mayinclude a band ranging from 700 nm to 1176 nm, a band ranging from 1333nm to 1818 nm, and/or a band ranging from 2000 nm to 2500 nm.

In another embodiment, the physiological constituent of interest may beblood oxygen saturation (O2sat). The O2sat may have a unique spectralprofile for wavelengths ranging from 400 nm to 2500 nm, which may bereferred to as a general band for O2sat. Narrower bands within thegeneral band for O2sat may be identified for which the O2sat may haveunique spectral profiles. The narrower bands may include a band rangingfrom 600 nm to 900 nm and from 1300 nm to 1800 nm. In embodimentstailored to measure O2sat, the filter 528 may include graphene, whichmay have a tunable passband ranging from 400 nm to 1800 nm.

In a specific embodiment, the filter 528 may include a linear variablefilter having a passband ranging from 908 nm to 1676 nm. The slope ofthe gradient may be 125 nm/mm+/−2.5 nm/mm. A half power bandwidth of thelinear variable filter may be less than 1% of a center wavelength of thelinear variable filter. Transmission of wavelengths within the passbandmay average to greater than or equal to 50 percent, whereas transmissionof out-of-band wavelengths may average tor less than or equal to 0.01percent for wavelengths ranging from 190 nm to 2500 nm. The linearvariable filter may include a thin film of indium gallium arsenidedeposited on an optical borosilicate-crown glass substrate. The linearvariable filter may have a surface quality of 60 to 40, and edge chipsmay be less than or equal to 0.25 mm.

In an embodiment, the filter 528 may include an absorptive filter. Anabsorptive filter may be formed to have distinct cutoff edges betweenregions of the absorptive filter corresponding to different wavelengthranges. Furthermore, an absorptive filter may be manufactured of adurable and/or flexible material. In an embodiment, the filter 528 mayinclude a three-dimensional structural interference filter. Thestructural interference filter may have a surface shape and/or aninternal grain boundary shape which may reflect some wavelengths oflight outside a passband of the filter 528 while transmitting otherswithin the passband of the filter 528. In an embodiment, the filter 528may include a dichroic filter, which may also be referred to as aninterference filter. The dichroic filter may be variable. The dichroicfilter may allow for very precise selection of wavelengths to be passedthrough the filter 528. For example, the dichroic filter may have atransmission profile with a narrow peak, such as a full width half max(FWHM) wavelength range of 50 nm, 40 nm, 30 nm, 25 nm, 20 nm, 10 nm, 5nm, and/or 1 nm. The dichroic filter may be implemented in embodimentswhere the filter 528 is incorporated into a sensor for measuringsensitive phenomena. The sensitive phenomena may include variousphysiological parameters, conditions, and/or constituents for whichsmall-percentage changes, such as less than or equal to a 50 percentchange, results in dramatically different outcomes. For example, thesensitive phenomenon may include a blood acidity level. A healthy bloodacidity may include a pH of 7.4. A blood pH less than or equal to 6.8 orgreater than or equal to 7.8 may result in irreversible cell damage. Inanother example, the sensitive phenomenon may include bone density.

In an embodiment, the filter 528 may include a grism. In an embodiment,the filter 528 may include a prism coupled to a diffraction grating. Asused herein, the grism or the coupled prism and diffraction grating maybe referred to as the grism. In various embodiments, the prism mayinclude a dispersion prism and/or a prismatic sheet, such as a Fresnelprism. In various embodiments, the diffraction grating may include aruled grating, a holographic grating, a transmission grating, areflective grating, a blazed holographic grating, a concave grating, anaberration corrected concave grating, a constant deviation monochromatorconcave grating, a Rowland type concave grating, a blazed holographicconcave grating, a sinusoidal holographic grating, a sinusoidal ruledgrating, a pulse compression grating, and so forth. In an embodiment,the diffraction grating may include a volume phase holographic (VPH)grating, which may have a high transmission percentage of impinginglight relative to other types of diffraction gratings. In an embodiment,the diffraction grating may diffract impinging light along onedimension.

In an embodiment, the diffraction grating may have a varying linespacing. For example, the line spacing of the diffraction grating mayincrease and/or decrease along a length and/or width of the diffractiongrating. In an embodiment, the lines of the diffraction grating may bealigned parallel to the width of the diffraction grating and/orperpendicular to the length of the diffraction grating. The line spacingmay be uniform along the width of the diffraction grating and may varyalong the length of the diffraction grating. In one embodiment, the linespacing may be uniform along the length of the diffraction grating andmay vary along the width of the diffraction grating. In anotherembodiment, the line spacing may vary along the length of thediffraction grating and may vary along the width of the diffractiongrating. In an embodiment, a blaze angle of the diffraction grating mayvary along the diffraction grating. The blaze angle may be uniform alongthe width of the diffraction grating and may vary along the length ofthe diffraction grating. The blaze angle may be uniform along the lengthof the diffraction grating and may vary along the width of thediffraction grating. The blaze angle may vary along the length of thediffraction grating and may vary along the width of the diffractiongrating. In an embodiment, varying the line spacing and/or the blazeangle may allow for spatial filtering of light by filtering differentwavelengths of light at different sections the filter 528.

A spatially varied diffraction grating (i.e. varying line spacing and/ordifferent blaze angle as described above) may allow for preciseselection of wavelengths to be filtered by the filter 528. The spatiallyvaried diffraction grating may be formed to filter a variety of rangesof wavelengths. The spatially varied diffraction grating may be formedwith discontinuities between the ranges of wavelengths. In anembodiment, the filter 528 may include the spatially varied diffractiongrating. The filter 528 may include a discontinuity between the firstregion 528 and the second region 528 b. The first region 528 a mayfilter out wavelengths outside a range of wavelengths from 400 nm to 450nm. The second region 528 b may filter out wavelengths outside a rangeof wavelengths ranging from 700 nm to 800 nm.

In an embodiment, the grism may be disposed between the collimator 530and the optical sensor 532. Light passed through the collimator 530 maystrike the grism within a range of angles of incidence where a median ofthe range may be a normal incidence. The diffraction grating mayseparate various constituent wavelengths of the light incident on thediffraction grating such that light leaving the diffraction grating at anormal angle may include all the wavelengths of the incident light, andthe separated constituent wavelengths of the impinging light may leavethe diffraction grating at non-normal angles. The prism may realign theseparated constituent wavelengths so that the separated constituentwavelengths may pass from the prism normal to a surface of the opticalsensor 532. In an embodiment, the collimator 530 may be disposed betweenthe grism and the optical sensor 532. The collimator 530 may absorband/or otherwise eliminate unseparated light passing from the grism. Forexample, the collimator 530 may include CNTs. The CNTs may have anaverage reflectance of less than or equal to 10 percent, less than orequal to 5 percent, less than or equal to 2 percent, less than or equalto 1 percent, less than or equal to 0.5 percent, and/or less than orequal to 0.2 percent. Accordingly, the CNTs may strongly absorb lightstriking the CNTs, making the collimator very “black.”

In one embodiment, the collimator 530 may include a device thatrestricts beam(s) of particles or waves passing into the first sensor112, such as light in visible and/or non-visible wavelengths, tospecific directions of motion, angles, or ranges of angles to becomemore aligned in a specific direction as the beam(s) travels through thefirst sensor 112. The collimator 530 may restrict a spatial crosssection of the beam(s). In an embodiment, the collimator 530 mayrestrict the beam(s) along one dimension and/or along two dimensions.

The filter 528 may have a length ranging from 5 mm to 9 mm, from 6 mm to9 mm, or from 7 mm to 9 mm. In an embodiment, the filter 528 may have alength of 7 mm, 7.35 mm, 7.5 mm, or 7.7 mm. The filter 528 may have awidth ranging from 0.5 mm to 2 mm, from 0.75 mm to 1.75 mm, or from 1 mmto 1.5 mm. In an embodiment, the filter 528 may have a width of 1.15 mm,1.35 mm, or 1.5 mm. The filter 528 may have a thickness ranging from 0.5mm to 3 mm, from 0.75 mm to 2.5 mm, or from 1 mm to 2 mm. In anembodiment, the filter may have a thickness of 1.25 mm, 1.5 mm, or 1.75mm.

The collimator 530 may be formed in one or more of a variety of ways. Invarious embodiments, the collimator 530 may be formed of one or moremicrotubes. In an embodiment, the collimator 530 may include a pluralityof microtubes, wherein each microtube is defined by one or more wallsencircling a through-channel. A microtube of the plurality of microtubesmay have a width ranging from 10 microns to 150 microns, and/or a heightranging from 30 microns to 500 microns. For example, the microtube mayhave a height equal to less than a thickness of 4 pages of printerpaper, and a width equal to less than a thickness of 1 page of printerpaper. The microtubes may be prepared separately and joined together,such as by a binder, or the microtubes may be prepared together. Forexample, the walls of the microtubes may be formed of CNTs. A catalystlayer may be patterned on a substrate forming an impression of theplurality of microtubes, and the CNTs may be grown on the catalystlayer, forming the walls encircling the through-channels to form themicrotubes. In another embodiment, the collimator 530 may include avolume of material through which through-channels and/or apertures areformed. The volume of material may, for example, include a photoresistmaterial. The through-channels and/or apertures may be etched throughthe photoresist material, such as by photolithography or plasma etching.

The collimator 530 may be positioned against the filter 528 and/or theoptical sensor. For example, the collimator 530 may be disposed betweenthe filter 528 and the optical sensor 532 as illustrated in FIG. 5A, orthe filter may be disposed between the collimator 530 and the opticalsensor 532 as illustrated in FIG. 5C. In an embodiment, one or more ofthe walls forming one or more of the microtubes of the collimator 530may be aligned normal to a surface of the filter 528 and/or a surface ofthe optical sensor 532. In an embodiment such as is shown in FIG. 5A,light may pass through the filter 528 and the collimator 530 may allowlight within a range of normal incidence passing from the filter 528 toimpinge on the optical sensor 532. In an embodiment such as is shown inFIG. 5C, the collimator 530 may allow light to impinge on the filter 528within a range of normal incidence. In an alternative embodiment, thecollimator wall may be aligned at a non-normal angle relative to thesurface of the filter 528 and/or the surface of the optical sensor 532.The angle may correspond to an angle of separated light leaving thefilter 528. For example, the filter 528 may include a diffractiongrating. Light may impinge on the diffraction grating at a normal angle.Separated light may leave the diffraction grating at a non-normal angle.The angle at which the wall of the collimator 530 is aligned to thefilter 528 and/or the optical sensor may match the angle correspondingto a first order of separated light leaving the diffraction grating,i.e. a diffraction maxima function equal to one, where the function isequal to an inter-grating spacing times the sine of a blaze angledivided by a wavelength of the light impinging on the diffractiongrating.

The collimator 530 may have a length ranging from 5 mm to 9 mm, from 6mm to 9 mm, or from 7 mm to 9 mm. In an embodiment, the collimator 530may have a length of 7 mm, 7.35 mm, 7.5 mm, or 7.7 mm. The collimator530 may have a width ranging from 0.5 mm to 2 mm, from 0.75 mm to 1.75mm, or from 1 mm to 1.5 mm. In an embodiment, the collimator 530 mayhave a width of 1.15 mm, 1.35 mm, or 1.5 mm. The collimator may have athickness ranging from 10 microns to 300 microns, from 20 microns to 250microns, or from 25 microns to 200 microns. In various embodiments, thesubstrate on which the collimator is grown may be incorporated with thecollimator into the first sensor 112. For example, the collimator may begrown on a borosilicate glass. The collimator substrate may have thesame length and width dimensions as the collimator. The collimatorsubstrate length and width dimensions may exceed the collimatordimensions by up to 2 mm, up to 1.5 mm, up to 1 mm, up to 0.5 mm, up to0.25 mm, up to 0.1 mm, or up to 0.05 mm. The collimator substrate mayhave a thickness ranging from 0.1 mm to 1.5 mm, from 0.25 mm to 1.25 mm,or from 0.5 mm to 1 mm.

The optical sensor 532 may be operable to convert light rays intoelectronic signals. For example, the optical sensor 532 may measure aphysical quantity of light at a defined wavelength or wavelength rangeand translate the measurement into a form that is readable by aprocessing device. The optical sensor 532 may include a semiconductor.The semiconductor may have one or more bandgaps corresponding to thedefined wavelength and/or wavelength range. The semiconductor may bearranged into an array, such as an array of pixels, corresponding toregions of the filter 528 such as the first region 528 a, the secondregion 528 b, and so forth. In various embodiments, the semiconductormay include an alloy of indium, gallium, phosphorus, and/or arsenic. Inone embodiment, the semiconductor may include an alloy of indiumarsenide, gallium arsenide, indium phosphide, and/or gallium phosphide.In one embodiment, the semiconductor may include lead(II) sulfide. Inyet another embodiment the semiconductor may include one or more sheetsof graphene. The semiconductor may be incorporated into a diode such asa photodiode. In another example, the optical sensor 532 may be atemperature sensor, a velocity liquid level sensor, a pressure sensor, adisplacement (position) sensor, a vibration sensor, a chemical sensor, aforce radiation sensor, a pH-value sensor, a strain sensor, an acousticfield sensor, an electric field sensor, a photoconductive sensor, aphotodiode sensor, a through-beam sensor, a retro-reflective sensor, adiffuse reflection sensor, and so forth.

The optical sensor 532 may include a segment such as a pixel. In anembodiment, the optical sensor 532 may include a plurality of thesegment, such as a plurality of pixels. The sensor segment may bealigned with a region of the filter 528 such as the first region 528 a,the second region 528 b, and so forth. The segment may have anidentifier such that the processing device may associate the segmentwith the region of the filter. The identifier may enable the processingdevice to determine a wavelength of light detected by the segment of theoptical sensor 532. For example, in one embodiment, the optical sensormay include a first sensor segment aligned with the first filter region528 a, a second sensor segment aligned with the second filter region 528b, and so forth. The first sensor segment may be identified by theprocessing device as detecting a wavelength and/or range of wavelengthsthat may pass unfiltered through the first filter region 528 a. Forexample, wavelengths ranging from 400 nm to 449 nm may pass unfilteredthrough the first filter region 528 a. The unfiltered light may strikethe first sensor segment, and the first sensor segment may, in responsegenerate an electrical signal that may be transmitted to the processingdevice. The processing device may identify the electrical signal asbeing transmitted by the first sensor segment and may identify thatsignals transmitted by the first sensor segment may be generated bylight having a wavelength ranging from 400 nm to 449 nm.

The optical sensor 532 may have a length ranging from 10 mm to 20 mm,from 12 mm to 18 mm, or from 14 mm to 16 mm. In an embodiment theoptical sensor 532 may have a length of 13.5 mm. The optical sensor 532may have a width ranging from 1 mm to 10 mm, from 2 mm to 8 mm, or from4 mm to 6 mm. In an embodiment, the optical sensor 532 may have a widthof 5.2 mm. The optical sensor 532 may have a thickness ranging from 0.5mm to 5 mm, from 1 mm to 3 mm, or from 1.5 mm to 2.5 mm. In anembodiment, the optical sensor 532 may have a thickness of 2 mm. Theoptical sensor 532 may include a photosensitive area and anon-photosensitive area. The photosensitive area may be smaller than thenon-photosensitive area. The photosensitive area may have a lengthranging from 5 mm to 9 mm, from 6 mm to 9 mm, or from 7 mm to 9 mm. Inan embodiment, the photosensitive area may have a length of 7 mm, 7.35mm, 7.5 mm, or 7.7 mm. The photosensitive area may have a width rangingfrom 0.5 mm to 2 mm, from 0.75 mm to 1.75 mm, or from 1 mm to 1.5 mm. Inan embodiment, the photosensitive area may have a width of 1.15 mm, 1.35mm, or 1.5 mm.

In an embodiment, regions of the filter 528, such as the linear variablefilter, may be correlated to regions of the optical sensor 532, such aspixels on the optical sensor, by exposing the optical sensor 532 to amonochromatic and/or narrowband light source via the filter 528. Themonochromatic light may strike the optical sensor 532 at a positioncorresponding to a location on the filter 528 through which the light istransmitted. A gradient and/or slope of the filter 528 may be used toextrapolate from the position on the optical sensor 532 themonochromatic light strikes which wavelengths will strike which pixels.For example, the monochromatic light may have a wavelength of 700 nm.The monochromatic light may pass through the filter 528 and strike afirst row of pixels. The filter 528 may have a gradient of 125 nm/mm. Asecond row of pixels one mm from the first row will be assigned awavelength band centered on 825 nm. A third row of pixels one mm fromthe second row will be assigned a wavelength band centered on 950 nm,and so forth. In one embodiment, the gradient and/or slope may bedetermined by exposing the filter 528 and the optical sensor 532 todifferent monochromatic light sources and identifying where on theoptical sensor 532 the monochromatic light sources strike, thencalculating the gradient based on the spacing between the positions andthe difference in wavelength of the monochromatic light sources.

A calibration file for the optical sensor 532 may be set based on whichpixel and/or set of pixels has the highest intensity. The calibrationfile for the optical sensor 532 may be set based on a curve fit to theintensities detected at a plurality of pixels. The curve may be comparedto a calculated shape of the curve and the difference may be included inthe calibration file to account for noise encountered duringcalibration.

In various embodiments, correlation of the filter 528 to the opticalsensor 532 may be done during manufacturing and/or testing of the firstsensor 112. Correlation may be done after the first sensor 112 isincorporated into the wearable device 100. The wearable device 100 maybe placed around a calibration material. The calibration material may betransparent and may reflect and/or transflect light towards the firstsensor 112. The light source 326 may be optically isolated from thefirst sensor 112 so that a substantial portion of light detected by thefirst sensor 112 is light reflected and/or transflected through thecalibration material. The isolation may reduce and/or eliminate noisefrom light passing directly from the light source 326 to the firstsensor 112. The calibration material may be selected to minimally absorblight. In an embodiment, the calibration material transmitsapproximately all light relevant to the correlation.

In various embodiments, correlation may be done during a user setupstage after an end user of the wearable device 100 obtains the wearabledevice 100. The wearable device 100 may include a calibration lightsource. The calibration light source may be positioned directly acrossthe wearable device 100 from the first sensor 112 as the wearable device100 is shaped in a shape corresponding to a shape of the wearable device100 as the wearable device 100 is being worn by the user. The wearabledevice 100 may be shaped into the as-worn shape off of the user suchthat an unimpeded, direct path is formed between the calibration lightsource and the first light sensor 112. The calibration light may emitlight directly towards the first sensor 112 and the filter 528 and theoptical sensor 532 may be correlated as described herein.

In one embodiment, the wearable device 100 may include a fiberoptic pathwithin and/or on the wearable device 100 between the light source 326and the first sensor 112. Correlation of the filter 528 to the opticalsensor 532 may include optically isolating the light source 326 from thefirst sensor 112 such that substantially all light emitted from thelight source 326 is blocked from the first sensor 112 except lighttransmitted via the fiberoptic path. The light transmitted via theoptical path may strike the optical sensor 532 via the filter 528. Theoptical sensor 532 and the filter 528 may be correlated as describedherein while the wearable device 100 is being worn by the user.

In one embodiment, the filter 528 may be integrated with the opticalsensor 532. For example, the optical sensor 532 may detect a discretewavelength and/or a narrow band of wavelengths. The optical sensor 532may include a photodiode having a large surface area, such as up to asame surface area as the first sensor 112. The discrete optical sensor532 may have an enhances signal to noise ratio to more accuratelyquantify a physiological constituent when compared with a smaller and/orbroader band embodiment of the optical sensor 532. In an embodiment, thenarrow band, large surface area optical sensor 532 may be used tocalibrate the first sensor 112.

In one embodiment, the filter 528, the collimator 530, and the opticalsensor 532 may be stacked together to form the first sensor 112. In oneexample, the filter 528, the collimator 530, and the optical sensor 532may be integrated together in a single sensor. In another example, thefilter 528, the collimator 530, and the optical sensor 532 may beinterconnected together. In one example, the filter 528, the collimator530, and the optical sensor 532 may be stacked vertically on top of eachother. In another embodiment, the filter 528 may be wedge shaped whereone end of the filter 528 has a relatively thick end that tapers to athinner edge. In one embodiment, the collimator 530 and the opticalsensor 532 may have relatively flat top surfaces and/or bottom surfaces.When the filter is a wedge shape, a filling material 534 may be attachedor affixed to the collimator 530 and/or the optical sensor 532 so thatthe filter 528 may rest or attach flush or level to the collimator 530and/or the optical sensor 532. In one example, the filling material 534may be an optically transparent material (such as clear glass or a clearplastic), an optically translucent material (such as polyurethane,colored or frosted glass, colored or frosted plastic, and so forth), orother material that does not interfere with defined wavelengths oflight. In another example, the filling materials 534 may be attached oraffixed to the collimator 530 and/or the optical sensor 532 by anadhesive, by welding, by friction, by a pressure fit, and so forth.

In a specific embodiment of the first sensor 112, the filter 528 and thecollimator 530 may be stacked on the photoreactive area of the opticalsensor 532. The optical sensor 532 may have a length of 13.5 mm, a widthof 5.2 mm, and a thickness of 2 mm. The photoreactive area of theoptical sensor 532 may have a length of 8 mm and a width of 1 mm. Thefilter 528 and the collimator 530 may have a length of 8 mm and a widthof 1 mm. The filter 528 may have a thickness of 1.5 mm. The collimator530 may have a thickness of 0.1 mm. Accordingly, the first sensor 112may have a length of 13.5 mm, a width of 5.2 mm, and a thickness of 3.1mm. In another specific embodiment, the collimator 530 may include thecollimator substrate, and the collimator substrate may have a thicknessof 0.5 mm. Accordingly, the collimator may have a thickness of 0.6 mm,and the first sensor 112 may have an overall thickness of 3.6 mm.

In one embodiment, a light source positioned at surface of a body partof an individual that is adjacent to a region of the body part where amuscular-walled tube is closest to an outer surface of the body part.The light source may transmit light within a wavelength range throughthe body part at a defined intensity and a defined depth to a secondlocation along the surface of the body part. In another embodiment, thecollimator 530 may be positioned at the second location along thesurface of the body part. The collimator may receive a portion of thelight. The collimator 530 may include a first microtube comprising acarbon nanotube tubular structure having a thickness between 1 micronand 10 microns and a height between 50 microns and 1000 microns. Thefirst microtube may absorb a first sub-portion of the portion of thelight that enters a tubular portion of the first microtube at a firstrange of angles and provide a channel for a second sub-portion of theportion of the light that enters the tubular portion of the firstmicrotube at a second range of angles to pass through the firstmicrotube. The collimator 530 may include the filter 528 attached to thecollimator 530 or the optical sensor 532. The filter 528 may be alignedwith the first microtube of the collimator 530 to filter out a definedwavelength or a defined wavelength range of the second sub-portion ofthe portion of the light. The collimator 530 may include a fillingmaterial 534 attached to the collimator or the filter 528 such that thefilter 528 attaches level to the collimator 530 or the optical sensor532. The filling material 534 may be an optically transparent material.The optical sensor 532 may attach to the collimator 530 or the filter528. The optical sensor 532 may measure an intensity of the secondsub-portion of the light that passes through the first microtube and thefilter 528.

In one example, the collimator 530 may include an array of microtubesthat includes the first microtube. In another example, the filter 528may be aligned with the array of microtubes to filter out differentwavelengths of second sub-portion of the portion of the light atdifferent locations of the filter 528. The optical sensor 532 maymeasure an intensity of the different wavelengths of second sub-portionof the portion of the light. In another example, the collimator 530 mayinclude a second microtube. A first portion of the filter 528 is alignedwith the first microtube to filter out a first wavelength of secondsub-portion of the portion of the light. A second portion of filter 528is aligned with the second microtube to filter out a second wavelengthof second sub-portion of the portion of the light. In another example,the optical sensor may measure the intensity of the first wavelength ofsecond sub-portion of the portion of the light that passes through thefirst microtube and/or measure the intensity of the second wavelength ofsecond sub-portion of the portion of the light that passes through thesecond microtube.

The carbon nanotube tubular structure may include: a first wall thatincludes a first set of carbon nanotubes infiltrated with carbon, asecond wall comprising a second set of carbon nanotubes infiltrated withcarbon, a third wall comprising a third set of carbon nanotubesinfiltrated with carbon, and a fourth wall comprising a fourth set ofcarbon nanotubes infiltrated with carbon, wherein the first wall, thesecond wall, the third wall, and the fourth wall form a square tubularstructure. The collimator 530 has a length between 5 mm and 9 mm and awidth between 0.5 mm and 2 mm. In another example, the carbon nanotubetubular structure may include a cylindrical wall comprising carbonnanotubes infiltrated with carbon. In another example, the carbonnanotube tubular structure may include a carbon-infiltrated carbonnanotube forest. The carbon-infiltrated carbon nanotube forest mayinclude a bundle of aligned carbon nanotubes. In another example, thefilter 528 may be a continuous gradient with spectral properties thatvary continuously along one dimension or plane of the filter 528 tofilter out light rays of different wavelengths based on where the lightrays strike along the surface of the filter 528.

In another example, the light transmitted from the light source passesdirectly from the light source to the collimator 530 or passesindirectly through a substance in the body part and be reflected towardsthe collimator 530. In another example, the carbon nanotube tubularstructure may include carbon nanotube material to absorb the portion ofthe light with an average reflectance of less than or equal to 10percent. In another example, the optical sensor 532 has a length rangingfrom 10 mm to 20 mm, a width ranging from 1 mm to 10 mm, a thicknessranging from 0.5 mm to 5 mm. In another example, the optical sensor 532may include a photosensitive area and a non-photosensitive area. Thephotosensitive area may have a length ranging from 5 mm to 9 mm and awidth ranging from 0.5 mm to 2 mm.

In another embodiment, the light source may be positioned at a firstlocation along a surface of a body part of an individual that isadjacent to a region of the body part where a muscular-walled tube isclosest to an outer surface of the body part. The light source maytransmit light to a second location along the surface of the body part.The collimator 530 may be positioned at the second location along thesurface of the body part. The collimator 530 may receive a portion ofthe light. The collimator 530 may include a first microtube comprising afirst carbon nanotube tubular structure. The first microtube may absorba first sub-portion of the portion of the light that enters a tubularportion of the first microtube at a first angle and/or provide a channelfor a second sub-portion of the portion of the light that enters thetubular portion of the first microtube at a second angle to pass throughthe first microtube. The filter 528 may be aligned with the firstmicrotube of the collimator 530 to filter out light at a definedwavelength or wavelength range of the second sub-portion of the portionof the light. The optical sensor 532 may be aligned with the collimator530 or the filter 528. The optical sensor 532 may measure an intensityof the second sub-portion of the light that passes through the firstmicrotube and the filter 528. In one example, the first carbon nanotubetubular structure may have a length between 5 mm and 9 mm and a widthbetween 0.5 mm and 2 mm. In another example, filling material 534attaches to the collimator 530 or the filter 528 such that the filter528 attaches level to the collimator 530 or the optical sensor 532. Thecollimator 530 may include a second microtube comprising a second carbonnanotube tubular structure. The second microtube may absorb a thirdsub-portion of the portion of the light that enters a tubular portion ofthe second microtube at a third angle and/or provide a second channelfor a fourth sub-portion of the portion of the light that enters thetubular portion of the second microtube at a fourth angle to passthrough the second microtube.

In another embodiment, the light source positioned at a first locationalong a surface of a body part of an individual. The light source maytransmit light to a second location along the surface of the body part.The collimator 530 positioned at the second location along the surfaceof the body part. The collimator 530 may include a microtube a tubularstructure. The microtube may absorb a first sub-portion of the portionof the light that enters a tubular portion of the microtube at a firstangle and/or provide a channel for a second sub-portion of the portionof the light that enters the tubular portion of the microtube at asecond angle to pass through the microtube. The filter 528 may bealigned with the microtube of the collimator 530 to filter out light ata defined wavelength or wavelength range of the second sub-portion ofthe portion of the light. The optical sensor 532 may be aligned with thecollimator 530. The optical sensor 532 may measure an intensity of thesecond sub-portion of the light that passes through the microtube andthe filter 528. The first location may be adjacent to a region of thebody part where a muscular-walled tube is closest to an outer surface ofthe body part. In one example, the microtube may be a carbon nanotubestructure. In another example, the light source may include a firstilluminator and a second illuminator. The filter 528 may include a firstsub-filter that is attached to the first illuminator and a secondsub-filter that is attached to the second illuminator.

FIG. 5B is a graph 538 of transmission profiles 538 a-e of the filter528, according to an embodiment. Some of the features in FIG. 5B are thesame as or similar to some of the features in FIGS. 1-5A as noted bysame reference numbers, unless expressly described otherwise. Thetransmission profiles 538 a-e may correspond to the filter regions 528a-e. For example: the transmission profile 538 a may represent a rangeof wavelengths and corresponding intensities of the wavelengths whichmay pass through the first filter region 528 a; the transmission profile538 b may represent a range of wavelengths and corresponding intensitiesof the wavelengths which may pass through the second filter region 528b; and so forth. In various embodiments, a passband corresponding to aparticular region may be sharp and/or narrow. For example, the firstfilter region 528 a may have a passband that may peak between 400 nm and405 nm, and a may have a FWHM band that may range from 395 nm to 410 nm.The filter 528 having at least one region with a sharp and/or narrowpassband. The sharp and/or narrow passband may correspond to a feature,such as a physiological condition, physiological parameter, and/orphysiological constituent, that may be indicated by reflection of anarrow range of wavelengths, such as a range of 20 nm, 15 nm, 10 nm, 5nm, 1 nm, and so forth.

FIG. 5C illustrates a side view of the first sensor 112, according to anembodiment. Some of the features in FIG. 5C are the same as or similarto some of the features in FIGS. 1-5B as noted by same referencenumbers, unless expressly described otherwise. The order that the filter528, the collimator 530, and the optical sensor 532 is not intended tobe limiting. In one example, as shown in FIG. 5A, the filter 528 may bestacked on top, the collimator 530 may be stacked in the middle, and theoptical sensor 532 may be stacked on the bottom. In another example, asshown in FIG. 5C, the collimator 530 may be stacked on top, the filter528 may be stacked in the middle, and the optical sensor 532 may bestacked on the bottom.

As discussed above, the collimator 530 may be a device that restrictsbeam(s) of particles or waves passing into the sensor to specificdirections of motion, angles, or ranges of angles to become more alignedin a specific direction. To restrict the beam(s), the collimator 530 mayinclude one or more microtubes 536 a-o that may extend from a topsurface of the collimator 530 to a bottom surface of the collimator 530.The microtubes 536 a-o may have various shapes, sizes, materials, orconfigurations to restrict the beam(s).

In various embodiments, one or more of the microtubes 536 a-o may bealigned over one or more of the filter regions 528 a-g. The microtube536 a may be aligned over the filter region 528 a. The microtubes 536b-c may be aligned over the filter region 528 b. The microtube 536 d maybe aligned over the filter regions 528 b-c. The region 536 e may bealigned over the filter regions 528 c-d. The microtubes 536 f-h may bealigned over the filter region 528 d. The microtube 536 i may be alignedover the filter regions 528 d-e. The microtube 536 j may be aligned overthe filter region 528 e. The microtubes 536 k-m may be aligned over thefilter region 528 f. The microtube 536 n may be aligned over the filterregions 528 f-g. The microtube 536 o may be aligned over the filterregion 528 g. Accordingly, light passing through one of the microtubes536 may pass through more than one region of the filter 528.

FIG. 5D illustrates an embodiment of the first sensor 112 with themicrotubes 536 a-o aligned directly with filter regions 528 b-f,according to an embodiment. Some of the features in FIG. 5D are the sameas or similar to some of the features in FIGS. 1-5C as noted by samereference numbers, unless expressly described otherwise. The microtubes536 a-c may be aligned over the filter region 528 b. The microtubes 536d-f may be aligned over the filter region 528 c. A wall between themicrotube 526 c and the microtube 536 d may be aligned with a boundarybetween the filter region 528 b and the filter region 528 c. Themicrotubes 536 g-i may be aligned over the filter region 528 d. A wallbetween the microtube 526 f and the microtube 536 g may be aligned witha boundary between the filter region 528 c and the filter region 528 d.The microtubes 536 j-1 may be aligned over the filter region 528 e. Awall between the microtube 526 i and the microtube 536 j may be alignedwith a boundary between the filter region 528 d and the filter region528 e. The microtubes 536 m-o may be aligned over the filter region 528f A wall between the microtube 526 l and the microtube 536 m may bealigned with a boundary between the filter region 528 e and the filterregion 528 f.

The optical sensor 532 may include a plurality of pixels. One or more ofthe pixels may be assigned, in software, a particular wavelengthcorresponding to a section of the filter 528 over the correspondingpixel and through which light may pass before striking the correspondingpixel. In an embodiment, a shape and/or alignment of the pixels may notmatch a shape of the contour line of filter 528. For example, thecontour line may be curved or non-perpendicular relative to the shape ofthe filter 528, and the pixels may be arranged rectangularly. The shapeof the gradient of the filter 528 may be determined by comparing shiftsin peak transmission intensities for neighboring rows of pixels runningperpendicular to the contour lines of the filter 528. The shifts may benoted in software and the pixels may be reassigned to correspond towavelengths according to the noted shift.

In various embodiments, walls separating and/or defining the microtubes536 a-o may be aligned with boundaries between the pixels. In variousother embodiments, at least some of the walls separating and/or definingthe microtubes 536 a-o may be aligned over at least some of the pixels.This may produce an aliasing effect, which may significantly reduce anintensity of light detected by the optical sensor 532. The aliasingeffect may be reduced by placing the collimator 530 at a sufficientdistance from the optical sensor 532. Light from neighboring microtubesmay bleed to areas beneath each other, reducing a shadow formed on thepixels by the walls between the microtubes 536 a-o. For example, lightpassing through microtube 536 a at an angle may strike a pixel beneathmicrotube 536 b. The separation distance between the collimator 530 andthe optical sensor 532 may be formed by the filter 528.

FIG. 6A illustrates a cross-sectional view of a light source 602emitting light rays 604 a-d into the first sensor 112, according to anembodiment. Some of the features in FIG. 6A are the same as or similarto some of the features in FIGS. 1-5D as noted by same referencenumbers, unless expressly described otherwise. In one embodiment, thelight source 602 may emit light, such as light rays 604 a-d. In oneexample, the light source 602 may emit the light rays 604 a-d toward thefirst sensor 112. In one embodiment, the light source 602 may emit thelight rays 604 a-d directly at the first sensor 112. In anotherembodiment, the light source 602 may emit the light rays 604 a-d at anobject and one or more of light rays 604 a-d may reflect off the objecttowards the first sensor 112.

The light source 602 may emit the light rays 604 a-d at different anglessuch that the light rays 604 a, 604 b, 604 c, and/or 604 d may directlyor indirectly encounter and/or pass into the first sensor 112 atdifferent angles. In one example, light ray 604 a may encountermicrotube 536 b of the collimator 530 at a first angle, where the lightray 604 a encounters a sidewall of the microtube 536 b such that thelight ray 604 a is absorbed by the sidewall. In another example, lightray 604 b may encounter microtube 536 g of the collimator 530 at asecond angle, where the light ray 604 b does not encounter a sidewall ofthe microtube 536 g and travels through the microtube 536 g to thefilter 528. In another example, light ray 604 c may encounter microtube536 h of the collimator 530 at a third angle, where the light ray 604 cdoes not encounter a sidewall of the microtube 536 h and travels throughthe microtube 536 h to the filter 528. In another example, light ray 604d may encounter microtube 536 h of the collimator 530 at a fourth angle,where the light ray 604 d encounters a sidewall of the microtube 536 hsuch that the light ray 604 d is absorbed by the sidewall.

In another embodiment, whether a light ray passes through one of themicrotubes 536 of the collimator 530 may be based on an angle that thelight ray enters the microtube 536 and a distance the light ray is froma sidewall of the microtube 536 as the light ray enters the microtube536. For example, light ray 604 a may enter microtube 536 b at arelatively steep angle such that the light ray 604 a strikes the sidewall of microtube 536 b. The steep angle may exceed, for example, 15degrees. In another example, the light ray 604 d may enter the microtube536 h at a relatively gradual angle (such as an angle of less than 15degrees) but the light ray 604 d may enter the microtube 536 h below athreshold distance from the sidewall of the microtube 536 h such thatthe light ray 604 d is absorbed by the sidewall. In another example,light ray 604 b may enter microtube 536 g and/or light ray 604 c mayenter microtube 536 h below the threshold angle and/or above thethreshold distance from the sidewalls of microtubes 536 g and 536 h suchthat the light rays 604 b and 604 c may not strike a sidewall of themicrotubes 536 g and 536 h and may pass through the microtubes 536 g and536 h to the filter 528. The number of light rays emitted from the lightsource 602, the number of light rays received at the collimator, theangle of the light rays, the size and/or shape of the collimator 530and/or the microtubes 536, and/or the wavelength or intensity of thelight rays are not intended to be limiting and may vary.

In another embodiment, to absorb the light rays that strike or impact asidewall of a microtube 536, the collimator 530 or at least a portion ofthe collimator 530 (such as the sidewalls of the collimator 530) mayinclude material that may absorb the light rays. In one embodiment, thematerial of the collimator 530 or a portion of the collimator 530 thatabsorbs the light rays may include carbon, CNTs, tungsten, nickel,UV-opaque plastic, UV-opaque photoresists, and so forth.

When the light rays 604 b and 604 c pass through the microtubes 536 gand 536 h of the collimator, the light rays 604 b and 604 c may thenpass through the filter 528 and/or the fill material, the filter 528 mayfilter out specific wavelengths of light and/or ranges of wavelengths atdifferent areas of the filter 528. In another example, the filter 528may be a linear variable filter or a continuously variable filter whosespectral properties vary continuously along one dimension or plane ofthe filter 528 to filter out light rays of different wavelengthsdepending on where the light rays strike along the surface of the filter528. Once the filter 528 filters out unwanted or non-desirablewavelengths of light, the remaining light rays at the wanted or desiredwavelengths may be received at the optical sensor 532. The light sensormay then measure the light intensity, the luminous intensity, or thepixel levels of the light rays received at the optical sensor 532. Theoptical sensor 532 may send data indicative of the measurements by theoptical sensor 532 to a processing device for the processing device toanalyze and determine various information. The various information maybe information associated with the light rays, information associatedwith an object the light rays are reflected off of, information aboutthe light source 602, and so forth.

FIG. 6B illustrates a perspective cross-sectional view of the lightsource 602 emitting the light rays 604 a-d into the first sensor 112,according to an embodiment. Some of the features in FIG. 6B are the sameas or similar to some of the features in FIGS. 1-6A as noted by samereference numbers, unless expressly described otherwise. As discussedabove, the light source 602 may emit light rays 604 a-d that may beabsorbed by the sidewalls of the microtubes 536 or pass through themicrotubes 536 of the collimator 530. In one embodiment, the light rays604 b and 604 c may pass through the microtubes 536 g and 536 h of thecollimator 530. As further discussed above, the filter 528 may be alinear variable filter, a continuously variable filter, a filter withdifferent bandpass filters that may filter out different wavelengths oflight at different locations along the surface of the filter 528. Forexample, the filter 528 may include the first region 528 a, the secondregion 528 b, the third region 528 c, the fourth region 528 d, the fifthregion 528 e, the sixth region 528 f, and the seventh region 528 g forfiltering different wavelengths of light or different wavelength rangesof light.

FIG. 6C illustrates a plurality of light sources 602 a-g positionedadjacent to the filter regions 528 a-g, according to an embodiment. Someof the features in FIG. 6C are the same as or similar to some of thefeatures in FIGS. 1-6B as noted by same reference numbers, unlessexpressly described otherwise. In an embodiment, the light source 602may include a plurality of illuminators 602 a-g. The filter 528 may bedisposed adjacent to the illuminators 602 a-g. In an embodiment, one ormore of the filter regions 528 a-g may be disposed adjacent to one ormore of the illuminators 602 a-g. For example, the filter region 528 amay be disposed adjacent to the illuminator 602 a; the filter region 528b may be disposed adjacent to the illuminator 602 b; and so forth. Inone embodiment, the filter regions 528 a-g may be integrated with theilluminators 602 a-g. In one embodiment, one or more of the illuminators602 a-g may be a broadband and/or a narrow band light source.

In one embodiment, one or more of the filter regions 528 a-g may be abroadband and/or a narrow band light source. For example, theilluminators 602 a-g may include a broadband light source emittingwavelengths ranging from 700 nm to 2500 nm, the filter region 528 a mayhave a passband ranging from 700 nm to 1000 nm, the filter region 528 bmay have a narrow passband ranging from 950 nm to 1250 nm, the filterregion 528 c may have a narrow passband ranging from 1200 nm to 1500 nm,the filter region 528 d may have a narrow passband ranging from 1450 nmto 1750 nm, the filter region 528 e may have a narrow passband rangingfrom 1700 nm to 2000 nm, the filter region 528 f may have a narrowpassband ranging from 1950 nm to 2250 nm, and/or the filter region 528 gmay have a narrow passband ranging from 2200 nm the 2500 nm. In anotherexample, the illuminators 602 a-g may include a first light sourceemitting wavelengths ranging from 700 nm to 1300 nm, a second lightsource emitting wavelengths ranging from 1300 nm to 1900 nm, and/or athird light source emitting wavelengths ranging from 1900 nm to 2500 nm.The illuminators 602 a-g may include a plurality of one or more of thebroadband light sources. For example, the illuminators 602 a-b mayinclude the first light source, the illuminators 602 c-d may include thesecond light source, and/or the illuminators 602 e-g may include thethird light source. The filter regions 528 a-g may include the passbandembodiments. The filter regions 528 a-b may be disposed adjacent to theilluminators 602 a-b; the filter regions 528 c-d may be disposedadjacent to the illuminators 602 c-d, and/or the filter regions 528 e-gmay be disposed adjacent to the illuminators 602 e-g. The foregoingwavelengths are provided as examples only, and are not intended to belimiting on the light sources and/or filters which may be incorporatedas described herein.

In an embodiment including multiple illuminators that emit differentranges of wavelengths, the optical sensor 532 may act as a time divisionmultiplexer. The processing device electronically coupled to theilluminators 602 a-g may pulse the illuminators 602 a-g at differenttimes, such as pulsing the illuminator 602 a at a first time, theilluminator 602 b at a second time, and so forth. The optical sensor 532may communicate intensities of light to the processing device. Todetermine wavelengths detected by the optical sensor 532, the processingdevice may correlate the intensities communicated by the optical sensor532 and the time the optical sensor 532 transmits signals with the timesthe illuminators 602 a-g were pulsed. The time may be an absolute time,such as a calendar time, or a relative time.

In an embodiment, the wearable device 100 may include a flexible bandsuch as the band 106, the light source 326, the optical filter 528, theoptical sensor 532, and the collimator 530. The flexible band may bedesigned to flex into a curvilinear shape, and may have a shape, size,and flexibility designed for attaching the flexible band to a wrist of auser. The wrist may include a dermal layer along an underside of thewrist and a blood vessel within the wrist adjacent to the dermal layeralong the underside of the wrist. The light source 326 may be embeddedin the flexible band. The light source 326 may emit light to interrogatethe wrist, the dermal layer, or the blood vessel. The light may includea constituent wavelength, where the constituent wavelength provides anindication of a state, condition, or constituent of the blood vessel ormaterial in the blood vessel by reflection from or transmission throughthe blood vessel or the material in the blood vessel. The light source326 may be positioned in the flexible band to emit, as the user wearsthe flexible band, the light towards the wrist. The optical filter 528may be integrated into the flexible band, and oriented in the flexibleband to isolate the constituent wavelength. The optical filter 528 mayhave a passband to isolate the constituent wavelength from otherwavelengths of the light. The optical sensor 532 may be integrated intothe flexible band and positioned in the flexible band to receive theconstituent wavelength. The optical sensor 532 may be is positioned inthe flexible band to receive, as the user wears the band, theconstituent wavelength through the wrist, the dermal layer, the bloodvessel, or the material in the blood vessel. The collimator 530 may beintegrated into the flexible band and may include: a glass substrate 606a substantially transparent to the constituent wavelength; a patternedthin film layer of iron patterned on the glass substrate and adhered tothe glass substrate; and a carbon nanotube grid structure 606 b coupledto the glass substrate 606 a. The patterned thin film layer of iron mayform a basis for the carbon nanotube grid structure 606 b. The carbonnanotube grid structure 606 b may be grown on the patterned thin filmlayer of iron. The collimator 530 may be positioned in the flexible bandto collimate the light before the light is received by the opticalsensor 532.

In an example of the embodiment, the carbon nanotube grid structure 606b may be grown upwards from a first surface of the glass substrate 606a. The glass substrate 606 a may be integrated into the flexible bandsuch that the first surface and the carbon nanotube grid structure 606 bare embedded within the band and a second surface of the glass substrate606 a opposite the first surface is flush with an inside surface of theflexible band, such as the inside surface 106 a of the band 106. Theglass substrate 606 a may form a hermetic seal with the flexible band,sealing the carbon nanotube grid structure 606 b, the optical filter528, or the optical sensor 532 within the flexible band.

In another example, the glass substrate 606 may include borosilicateglass. The borosilicate glass may be scratch resistant to protect thecollimator 530, the optical filter 528, and/or the optical sensor 532,and to minimize interference with the light by scratches to the glasssubstrate 606. The carbon nanotube grid structure 606 b may include: awall having a height ranging from 30 microns to 500 microns; and/or athrough-channel having a width ranging from 10 microns to 150 microns.The collimator 530 and the optical filter 528 may be stacked together inthe flexible band. The carbon nanotube grid structure 606 b may bepositioned between the glass substrate 606 a and the optical filter. Thecollimator 530 and the optical sensor 532 may be stacked together in theflexible band. The carbon nanotube grid structure 606 b may bepositioned between the glass substrate 606 a and the optical sensor 532.

In another example, the collimator 530 may include an adhesive adheringthe carbon nanotube grid structure 606 b to the glass substrate 606 a.The adhesive may be transparent to the constituent wavelength, and/orthe adhesive may couples the carbon nanotube grid structure 606 b to theglass substrate 606 a. The adhesive may be patterned to match a patternof the carbon nanotube grid structure 606 b on the glass substrate 606a. In another example, the glass substrate 606 a may include a patternedetch. A pattern of the patterned etch may match the carbon nanotube gridstructure 606 b. The carbon nanotube grid structure 606 b may bepositioned in the patterned etch in the glass substrate 606 a. Inanother example, the glass substrate 606 a may include a thicknessranging from 300 microns to 3 millimeters.

In another example, the optical filter 528 may include a thin filmlinear variable filter. The thin film linear variable filter may bedeposited on a first side of the glass substrate 606 a. The collimator530 may be is positioned on a second side of the glass substrate 606 aopposite the first side of the glass substrate 606 a. In anotherexample, the glass substrate 606 a may include a dye having the passbandto allow the constituent wavelength to pass through the glass substrate606 a unattenuated.

In an embodiment, the wearable device 100 may include the band 106, thelight source 326, the optical sensor 532, the optical filter 528, andthe glass substrate 606 a. The band 106 may have a shape, size, andflexibility designed for attaching the band 106 to a body part of auser. The light source 326 may be embedded in the band 106. The lightsource 326 may emit light to interrogate the body part, the lightcomprising a constituent wavelength that provides and indication of afeature of the body part. The light source 326 may be is positioned inthe band 106 to emit, as the user wears the band 106, the light towardsthe body part. The optical sensor 532 may be integrated into the band106 and positioned in the band 106 to receive the constituentwavelength. The optical sensor 532 may be positioned in the band 106 toreceive, as the user wears the band 106, the constituent wavelengththrough the body part. The glass substrate 606 a may be integrated intothe band 106 and oriented in the band 106 to receive the light throughthe body part as the user wears the band 106. The glass substrate 606 amay include a grid structure etched into the glass substrate and carbonnanotubes disposed in the grid structure forming walls of the gridstructure.

In an example of the embodiment, the etching of the grid structure mayform an adhesion surface for the carbon nanotubes, the carbon nanotubesadhered to the grid structure. The carbon nanotubes may be grown upwardsfrom a first surface of the glass substrate 606 a relative to ahorizontal plan. The glass substrate 606 a may be flipped over relativeto the horizontal plane and the carbon nanotubes may integrated into theband 106 facing downwards relative to the horizontal plane.

In another example, the optical filter 528 and the glass substrate 606 amay be ordered in the band 106 so that the light passes, as the userwears the band 106, from the body part through the optical filter 528before passing through the grid structure. The light may be filteredinto the constituent wavelength before the constituent wavelength iscollimated and passed to the optical sensor 532. The glass substrate 606a and the optical filter 528 may be ordered in the band 106 so that thelight passes, as the user wears the band 106, from the body part throughthe grid structure before passing through the optical filter 528. Thelight may be collimated before being filtered into the constituentwavelength and passing to the optical sensor 532.

In another example, an etch pattern of the grid structure may correlatewith a pixel structure of the optical sensor 532. The walls of the gridstructure may be aligned with boundaries between individual pixels ofthe optical sensor 532. The grid structure etched into the glasssubstrate may have a varying thickness, the walls having a correspondingvarying thickness.

In an embodiment, the wearable device 100 may include the band 106, thelight source 326, the optical sensor 532, and the glass substrate 606 a.The band 106 may have a shape, size, and flexibility designed forattaching the band 106 to a body part of a user. The light source 326may be embedded in the band 106. The light source 326 may emit light tointerrogate the body part, the light including a constituent wavelengththat provides an indication of a feature of the body part. The lightsource 326 may be positioned in the band 106 to emit, as the user wearsthe band 106, the light towards the body part. The optical sensor 532may be integrated into the band 106 and positioned in the band 106 toreceive the constituent wavelength. The optical sensor 532 may bepositioned in the band 106 to receive, as the user wears the band 106,the constituent wavelength through the body part. The glass substrate606 a may be integrated into the band 106 and oriented in the band 106to receive the light through the body part as the user wears the band106. The glass substrate 606 a may include the optical filter 528 andthe carbon nanotube grid structure 606 b. The optical filter 528 mayisolate the constituent wavelength from the light, where the opticalfilter 528 has a passband to isolate the constituent wavelength fromother wavelengths of the light. The carbon nanotube grid structure 606 bmay include walls and through-channels, and may be adhered to the glasssubstrate 606 a. The optical filter 528 may be positioned on a firstside of the glass substrate 606 a and the carbon nanotube grid structure606 b may be positioned on a second side of the glass substrate 606 aopposite the first side of the glass substrate 606 a.

FIG. 7A illustrates an embodiment of a collimator arranged in a firsttwo-dimensional (2D) array 702, according to an embodiment. Some of thefeatures in FIG. 7A are the same as or similar to some of the featuresin FIGS. 1-6C as noted by same reference numbers, unless expresslydescribed otherwise. In an embodiment, the collimator may be thecollimator 530. The collimator may include a cylindrical microtube 704.The cylindrical microtube 704 may be the same as or similar to themicrotubes 536 a-o. A plurality of the cylindrical microtube 704 mayform the first two-dimensional array 702. The first 2D array 702 mayinclude a rows 712 and/or columns 714. For example, the first 2D array702 may include 7 rows 712 and/or 7 columns 714. The cylindricalmicrotube 704 may be circular. A number of the rows 712 may equal anumber of the columns 714. The circular cylindrical microtubes 704 maybe aligned such that the collimator may be square-shaped. The circularcylindrical microtubes 704 may be aligned such that the collimator maybe trapezoid-shaped. One or more of the plurality of cylindricalmicrotubes 704 may have an ellipsoid cross-sectional shape such that, asa number of the rows 712 equals a number of the columns 714, thecollimator may form a rectangle. In various embodiments, the first 2Darray 702 may form any of a variety of geometric and/or non-geometricshapes, such as a square, a rectangle, a diamond, a parallelogram, atrapezoid, a polygon, a circle, a geometric pattern, a fractal geometry,and so forth.

A number of cylindrical microtubes 704 in the rows 712 and/or thecolumns 714 may vary according to the shape of the first 2D array 702.For example, a first row of the rows 712 may have 7 cylindricalmicrotubes 704, a second row of the rows 712 adjacent to the first rowmay have 8 cylindrical microtubes 704, a third row of the rows 712adjacent to the second row may have 6 cylindrical microtubes 704, and soforth. In an embodiment, a first column of the columns 714 may have 100cylindrical microtubes 704, a second column of the columns 714 adjacentto the first column may have 105 cylindrical microtubes 704, a thirdcolumn of the columns 714 adjacent to the second column may have 113cylindrical microtubes 704, and so forth.

In one embodiment, each cylindrical microtube 704 may have similar orthe same dimensions. In another embodiment, some cylindrical microtubes704 may have different dimensions than other cylindrical microtubes 704.For example, some cylindrical microtubes 704 may have a different heightthan other cylindrical microtubes 704. In another example, somecylindrical microtubes may have different diameters than othercylindrical microtubes 704. In some embodiments, a dimension of thecylindrical microtubes 704 may correspond to a filter region over whichthe cylindrical microtubes 704 may be disposed. The filter region mayhave a passband of wavelengths. The dimension of the cylindricalmicrotubes 704 may correspond to the passband.

In an embodiment, the cylindrical microtube 704 may be defined by a wall704 a encompassing a through-channel 704 b. The wall 704 a may be formedof one or more nanotubes. In an embodiment, the wall 704 a may be formedof a forest of nanotubes. The nanotube may include a CNT. The CNT may bea single-walled CNT (SWCNT), a double-walled CNT (SWCNT), and/or amulti-walled CNT (MWCNT). The nanotube forest may include one or moreSWCNTs, DWCNTs, and/or MWCNTs. The nanotubes may be aligned to form thewall 704 a. In an embodiment, the nanotubes may be aligned along alength of the wall 704 a, a height of the wall 704 a (such as may bedescribed and/or illustrated regarding FIG. 11B), and/or a width of thewall 704 a. The nanotube forest may be infiltrated with a bolsteringmaterial, where “bolster” may refer to a property of a material thatincreases resistance against an applied force of the material and/oranother material with which the material is incorporated. In variousembodiments, the bolstering material may include a metal such as gold,silver, platinum, iron, nickel, cobalt, and so forth. In an embodiment,the bolstering material may include carbon. In an embodiment, thebolstering material may include graphene.

In an embodiment, the collimator may be integrated into a sensor, suchas the first sensor 112. The sensor may include the collimator and afilter, such as the filter 528. A number and/or arrangement of theplurality of cylindrical microtubes 704 may correspond to a shape of aboundary of the filter. The filter may include one or more boundariescorresponding to a transition within the filter from a one region toanother region, which may be referred to as a filter region boundary.For example, the filter 528 includes the first region 528 a and thesecond region 528 b. A transition point from the first region 528 a tothe second region 528 b may represent an embodiment of the filter regionboundary. Accordingly, the regions of the filter may have a shape, and ashape of the filter region boundary may correspond to one or more of thefilter region shapes. The arrangement of the plurality of cylindricalmicrotubes 704 may, in an embodiment, align a first set of the pluralityof cylindrical microtubes 704 over the first filter region and a secondset of the plurality of cylindrical microtubes 704 over the secondfilter region adjacent to the first set of the plurality of cylindricalmicrotubes 704. A boundary between the first set of the plurality ofcylindrical microtubes 704 and the second set of the plurality ofcylindrical microtubes 704 may have a shape the same as or similar tothe shape of the filter region boundary.

In one embodiment, the filter may have a thickness that varies along alength of the filter, which may be referred to as a gradient of thefilter. The filter may include a continuous line running perpendicularto the gradient having a fixed thickness, which may be referred to as acontour line. The filter region may correspond to a segment of thelength of the filter with a fixed change in thickness over the segmentthat corresponds to a range of wavelengths that pass through the filterregion. In an embodiment, the filter region boundary may be formed bythe contour line between the first region and the second region. Thecontour line may be straight, curved, linear, non-linear, and so forth.The arrangement of the plurality of cylindrical microtubes 704 may, inan embodiment, align the boundary between the first set of the pluralityof cylindrical microtubes 704 and the second set of the plurality ofcylindrical microtubes 704 with the contour line.

In an embodiment, alignment of the boundary between the first set of theplurality of cylindrical microtubes 704 and the second set of theplurality of cylindrical microtubes 704 with the contour line mayincrease precision of measurement. The filter may have limitations toprecision from defects and/or limitations in a manufacturing process ofthe filter. The limitations may include the contour line being jagged,curved, and/or non-linear, and/or the contour-line not beingperpendicular with an outside edge of the filter. In variousembodiments, decreasing and/or eliminating the defects and orlimitations of the filter may be associated with increasing costs ofpreparing the filter. Aligning the cylindrical microtube 704 boundarywith the contour line may allow for similar precision using a low-costfilter as may be achieved using a high-cost filter. If a high-costfilter does not achieve a sufficient precision, aligning the cylindricalmicrotube 704 boundary with the contour line may allow for increasedprecision of the miniaturized spectrometer using the high-cost filter.Additionally, aligning the cylindrical microtube 704 boundary with thecontour line may improve a precision of the miniaturized spectrometer bysegmenting collimated light to specific regions of the filter.Furthermore, in various embodiments, the cylindrical microtubes may bemisaligned with the contour line.

In an embodiment, the cylindrical microtube 704 may have a lengthwiseshape 716. The lengthwise shape 716 of the cylindrical microtube 704 maydefine a height of the cylindrical microtube 704. The lengthwise shape716 may be formed by the wall 704 a. The lengthwise shape 716 may bestraight, curved, linear, non-linear, and so forth. In an embodiment,the curved and/or non-linear lengthwise shape 716 of the cylindricalmicrotube 704 may reduce an intensity of light passing through thecylindrical microtube 704, and/or may increase alignment of light rayspassing through the cylindrical microtube 704 and therefore thecollimation function of the collimator. In an embodiment, the wall 704 amay have a uniform or a non-uniform thickness. The non-uniform thicknessof the wall 704 a may define the lengthwise shape 716.

In another embodiment, the wall 704 a may have a surface roughness. Thesurface roughness may define the lengthwise shape 716. The surfaceroughness of the wall 704 a may be controlled during a preparationprocess of the wall 704 a. For example, in an embodiment including CNTs,the surface roughness of the wall 704 a may be directly related to athickness of a catalyst layer on which the CNTs are grown. In anembodiment, a greater surface roughness of the wall 704 a may reduce areflectivity and/or a reflectance of the wall 704 a, thereby increasingthe collimation function of the collimator. In an embodiment of the wall704 a including infiltrated CNTs, the reflectivity and/or reflectance ofthe wall 704 a may be reduced by reducing the infiltration. In anotherembodiment, the wall 704 a may be etched, such as by plasma etching, toincrease the roughness of the wall 704 a and/or reduce the reflectivityand/or reflectance of the wall 704 a.

FIG. 7B illustrates an embodiment of the collimator arranged in a second2D array 706, having a square microtube 708. Some of the features inFIG. 7B are the same as or similar to some of the features in FIGS. 1-7Aas noted by same reference numbers, unless expressly describedotherwise. The square microtube 708 may be the same as or similar to themicrotubes 536 a-o. The second 2D array 706 may include a plurality ofthe square microtube 708. The second 2D array 706 may include the rows712 and/or the columns 714. For example, the second 2D array 706 mayinclude 15 of the rows 712 and/or 3 of the columns 714.

A length of the second 2D array 706 may be greater than a width of thesecond 2D array 706, or vice versa. This may be due to the number ofrows 712 being greater than the number of columns 714, or vice versa. Inan embodiment, the relative dimensions of the second 2D array 706 maycorrespond to a shape of the sensor into which the collimator may beintegrated, and/or a shape of an electronic device into which thecollimator and/or the sensor may be integrated. For example, the second2D array 706 may be integrated into a sensor such as the first sensor112. The sensor 112 may be integrated into a band of a wearable device,such as the band 106 of the wearable device 100. The band may have alength greater than a width of the band. Accordingly, the relativedimensions of the second 2D array 706 may correspond to the relativedimensions of the band.

In another embodiment, the relative dimensions of the second 2D array706 may correspond to relative dimensions of a structure the sensor intowhich the second 2D array 706 is integrated may take measurements from.For example, the sensor may take measurements of light reflected from asegment of a vein and/or an artery. The segment may have a lengthgreater than a diameter of the segment. The second 2D array 706 may havea length the same as or approximately the same as the segment length.The second 2D array 706 may have a width the same as or approximatelythe same as the segment diameter. In another example, the second 2Darray 706 may have a width greater than the segment diameter by up to100 percent, up to 75 percent, up to 50 percent, up to 40 percent, up to30 percent, up to 25 percent, up to 20 percent, up to 15 percent, up to10 percent, and/or up to 5 percent. The larger width of the second 2Darray 706 compared to the segment diameter may increase an amount oflight captured by the second 2D array 706 that may be reflected from thesegment. The sensor may have similar dimensions as the second 2D array706. In yet another example, the second 2D array 706 may have a widthsmaller than the segment diameter by up to 5 percent, up to 10 percent,up to 15 percent, up to 20 percent, up to 25 percent, up to 30 percent,up to 40 percent, up to 50 percent, and/or up to 75 percent. The smallerwidth of the second 2D array 706 compared to the segment diameter maymaximize an amount of light the second 2D array 706 captures that may bereflected by the segment compared to an amount of light the second 2Darray 706 captures that may be reflected by another structure.

The concepts and/or details of the foregoing discussion regarding thesecond 2D array 706 may similarly apply to the first 2D array 702discussed and illustrated regarding FIG. 7A, embodiments of microtubeshaving different shapes other than circular or square, the collimator530 described and illustrated herein, and/or the first sensor 112described and illustrated herein.

FIG. 7C illustrates an embodiment of the collimator arranged in a third2D array 710, including the square microtube 708 illustrated in FIG. 7B,according to an embodiment. Some of the features in FIG. 7C are the sameas or similar to some of the features in FIGS. 1-7B as noted by samereference numbers, unless expressly described otherwise. The third 2Darray 710 may include a plurality of the square microtube 708. The third2D array 710 may include the rows 712 and/or the columns 714. In oneembodiment, the third 2D array 710 may include 5 of the rows 712 and/or3 of the columns 714. The concepts and/or details of the discussionabove regarding the second 2D array 706 may similarly apply to the third2D array 710.

FIG. 8 illustrates the second 2D array 706 illustrated in FIG. 7B,further including a filler 802, according to an embodiment. Some of thefeatures in FIG. 8 are the same as or similar to some of the features inFIGS. 1-7C as noted by same reference numbers, unless expresslydescribed otherwise. The filler 802 may be disposed within the microtube708. The filler 802 may fill the microtube 708 such that the filler maybe flush with a top edge of the microtube 708. The filler 802 may form acontinuous surface with the top edge 804 of the microtube 708. In anembodiment, the filler 802 may form a filler surface over the top edge804 of the microtube 708. In an embodiment, the filler 802 may for thefiller surface over a bottom edge 806 of the microtube 708. In anembodiment, the filler 802 may coat a wall 808 of the microtube 708. Inan embodiment, the filler 802 may surround the microtube 708 and/or thesecond 2D array 706. In an embodiment, the continuous surface and/or thefiller surface may be smooth relative to a filter, such as the filter528, and/or a sensor, such as the optical sensor 532. The filler 802 mayenable a smooth interface between the collimator, the filter, and/or thesensor. The smooth interface may minimize scattering of light.Furthermore, the filler 802 may prevent debris from occluding themicrotube 708. Additionally, the filler 802 may increase a rigidity ofthe second 2D array 706 and/or a resistance of the second 2D array 706to one or more forces that may deform and/or break the second 2D array706.

In various embodiments, the filler 802 may include a polymer that may berigid and transparent to wavelengths of light to be detected by theoptical sensor. The polymer may have low viscosity in a liquid and/orresin state to prevent damaging the microtubes 708 as the polymer isdeposited on the 2D array 706. The filler 802 may be added to the second2D array 706 by a process corresponding to a type of material of whichthe filler 802 is made. For example, in an embodiment including thepolymer, the second 2D array 706 may be dipped in a volume of moltenpolymer to coat the second 2D array 706 in the polymer. In anembodiment, the filler 802 may be sprayed and/or spun onto the second 2Darray 706. In one embodiment, a liquid resin may be poured over thesecond 2D array 706. The second 2D array 706 and resin may be placedinto a vacuum chamber and the pressure inside the chamber may be reduceduntil air bubbles form in the resin and seep out of the resin. The 2Darray 706 and resin may remain in the vacuum until all air has escapedthe 2D array and resin. The pressure inside the chamber may be graduallyincreased back towards atmospheric pressure to press the resin into themicrotubes 708. The resin may then be cured and/or cross-linked byexposer to hear and/or UV light to solidify the resin.

Materials for forming a miniaturized spectrometer, such as the firstsensor 112, may be selected to minimize a difference in a refractiveindex between layers of the miniaturized spectrometer. The layers mayinclude the collimator, the filter, and/or an optical sensor, such asthe optical sensor 532. At an interface between the collimator and thefilter, refraction of light passing through the layers may occur due toa difference in the respective refractive indices of the layers. Therefraction may decrease an intensity of the light as the light impingeson the sensor. An amount of refraction as light transitions across thecollimator-filter interface may correspond directly to the differencethe respective indices of refraction of the collimator and the filter.Minimizing refraction across the collimator-filter interface may includematching as closely as possible the collimator index of refraction andthe filter index of refraction. In various embodiments, the filter mayhave an index of refraction ranging from 1.4 to 2.0. In variousembodiments, the filler 802 of the collimator may have an index ofrefraction ranging from 1.3 to 1.9. In a specific embodiment, the filtermay have an index of refraction of 1.7. A polymeric compound may beselected for the filler 802 having an index of refraction of 1.7. Theindex of refraction of the filter and/or the polymeric compound may varyfor differing wavelengths. Accordingly, materials may be selected forthe filter and/or the polymeric compound such that the differencebetween the filter index of refraction and the polymeric compound indexof refraction a selected range of wavelengths may be minimized.

Materials for forming one or more of the layers of the miniaturizedspectrometer may be selected based on a reflectivity, respectively, ofthe materials. Minimizing the reflectivity of the materials may maximizean intensity I_(trans) of impinging light transmitted through variousinterfaces between the layers and/or other media, such as air or a bodytissue. The reflectance of the materials may vary for differingwavelengths. Accordingly, materials may be selected for the filterand/or the filler 802 which may, for wavelengths within a range from 400nm to 450 nm, for wavelengths within a range from 725 nm to 775 nm, forwavelengths within a range from 1050 nm to 1100 nm, and/or forwavelengths within a range from 1550 nm to 1700 nm, have a reflectanceless than or equal to 10%, less than or equal to 5%, and/or less than orequal to 1%.

In various embodiments, the filler 802 may filter light passing throughthe microtubes 708. For example, light impinging on the filler 802 at afirst end of the microtubes 708 may have an initial spectral profile,which may include various wavelengths of various intensities. Lightleaving the filler 802 at a second end of the microtubes 708 may have afiltered spectral profile, which may include a wavelength having a peakintensity with other wavelengths having significantly reduced and/oreliminated intensities. The filler 802 may include a dye for filteringthe light. The filler 802 may have a surface structure which may induceinterference and thereby filter the light. The filler 802 may include adichroic filter.

The filler 802 may be integrated into embodiments of the collimator 530having cylindrical microtubes. Inter-tube channels may be formed betweenthe microtubes of the array 702. The inter-tube channels may be filledwith the filler 802.

In an embodiment, the collimator 530 may include a first carbon nanotubestructure, a second carbon nanotube structure, and the filler 802. Thefirst carbon nanotube structure may include a first microtube thatincludes a first set of aligned carbon nanotubes infiltrated by carbonand a first through-channel and have a height to through-channel widthaspect ratio between 3:1 to 10:1. The first set of aligned carbonnanotubes infiltrated by carbon may be configured to absorb a firstportion of light that travels through the first through-channel at afirst angle and impinges a side of a first through-channel portion. Thefirst set of aligned carbon nanotubes infiltrated by the carbon may beconfigured to allow a second portion of the light that enters the firstthrough-channel at a second angle to pass through from a top of thefirst through-channel to a bottom of the first through-channel. Thesecond carbon nanotube structure may include a second microtube thatincludes a second set of aligned carbon nanotubes infiltrated by carbonand a second through-channel. The second carbon nanotube structure mayhave a height to through-channel width aspect ratio between 3:1 to 10:1.The second set of aligned carbon nanotubes infiltrated by carbon may beconfigured to absorb a third portion of the light that travels throughthe second through-channel at a third angle and impinges a side of asecond through-channel portion. The second set of aligned carbonnanotubes infiltrated by the carbon may be configured to allow a fourthportion of the light that enters the second through-channel at a fourthangle to pass through from a top of the second through-channel to abottom of the second through-channel. The first microtube and the secondmicrotube may share a common structural portion to form an array ofmicrotubes. The filler 802 may be disposed within the firstthrough-channel or the second through-channel. The filler 802 may fillthe first through-channel from a bottom of the first through-channel orthe second through-channel to a top of the first through-channel or thesecond through-channel such that the filler 802 is flush with a bottomsurface, i.e. the bottom edge 806, of the first through-channel or thesecond through-channel and a top surface, i.e. the top edge 804, of thefirst through-channel or the second through-channel. The filler 802 maybe a transparent material to allow light to be transmitted through thefirst through-channel or the second through-channel without interferingwith the light.

In an example of the embodiment, the first angle, the second angle, thethird angle, or the fourth angle of the light is relative to a planeextending along the bottom surface of the collimator 530. The firstangle or the second angle may correlate directly with the first carbonnanotube structure aspect ratio. The third angle or the fourth angle maycorrelate directly with the second carbon nanotube structure aspectratio. The first angle or the third angle may range up to 85 degrees, upto 80 degrees, up to 75 degrees, up to 70 degrees, or up to 60 degrees.The second angle or the fourth angle may range from 85 degrees to 90degrees, from 80 degrees to 90 degrees, from 75 degrees to 90 degrees,from 70 degrees to 90 degrees, or from 60 degrees to 90 degrees. Adegree of the first angle or the second angle may be based a distance aray of the first portion of light is from a wall of a first carbonnanotube structure.

In another example, the first carbon nanotube structure may include: afirst wall comprising a first subset of carbon nanotubes infiltratedwith carbon; a second wall comprising a second subset of carbonnanotubes infiltrated with carbon; a third wall comprising a thirdsubset of carbon nanotubes infiltrated with carbon; and a fourth wallcomprising a fourth subset of carbon nanotubes infiltrated with carbon.A thickness of the first wall may be different than a thickness of thesecond wall.

In another example, the collimator 530 may have a length between 5 mmand 9 mm and a width between 0.5 mm and 2 mm. The array of microtubesmay include a plurality of microtubes, including the first microtube andthe second microtube, that share common structural portions to form thesquare or rectangular array of microtubes 706. The first carbon nanotubestructure may include a cylindrical wall of the first set of alignedcarbon nanotubes forming a cylindrical microtube.

In another example, the carbon nanotube structure may include carbonnanotube material to absorb the first portion of the light with anaverage reflectance of less than or equal to 10 percent.

In an embodiment, the collimator 530 may include a carbon nanotubestructure, and the filler 802. The carbon nanotube structure may includea microtube that includes a set of aligned carbon nanotubes infiltratedby carbon and a through-channel. The set of aligned carbon nanotubesinfiltrated by carbon may be configured to absorb a first portion oflight that travels through the through-channel at a first angle andimpinges a side of a through-channel portion. The set of aligned carbonnanotubes infiltrated by the carbon may be configured to allow a secondportion of light that enters the through-channel at a second angle topass through from a top of the through-channel to a bottom of thethrough-channel. The filler 802 may be disposed within thethrough-channel. The filler 802 may fill the through-channel from abottom of the through-channel to a top of the through-channel such thatthe filler 802 is flush with the bottom surface of the through-channeland the top surface of the through-channel. The filler 802 may be atransparent material to allow light to be transmitted through thethrough-channel without interfering with the light.

In an example of the embodiment, the filler 802 may be a polymer with arelatively low viscosity such that a resin of the polymer is configuredto be deposited in the through-channel without damaging the microtube.The filler 802 may reinforce the microtube to increase a rigidity of thecarbon nanotube structure. The filler 802 may have an index ofrefraction ranging from 1.3 to 1.9 based on a wavelength of lighttraveling through the through-channel.

In another example, the set of aligned carbon nanotubes infiltrated bycarbon may form the wall 808 with a thickness ranging from 1 micron to50 microns and the height 7016 ranging from 50 microns to 1000 microns.

In another example, the infiltration of the carbon into the set ofaligned carbon nanotubes may create a roughness along a surface of themicrotube. The roughness may be defined by lengthwise shape of thesurface of the microtube. The surface roughness of the microtube mayreduce a reflectivity of the surface of the microtube.

In an embodiment, the collimator 530 may include a carbon nanotubestructure having a microtube that includes a set of aligned carbonnanotubes infiltrated by carbon and a through-channel. The carbonnanotube structure may have a defined height to through-channel widthaspect ratio. The defined height to through-channel width aspect ratiomay be based on a defined collimation to diffraction ratio. As thedefined height to through-channel width aspect ratio increases light,collimation by the collimator may increase and diffraction by thecollimator may decrease. The set of aligned carbon nanotubes infiltratedby carbon may be configured to absorb a first portion of light thattravels through the through-channel at a first angle and impinges a sideof a first through-channel portion. The set of aligned carbon nanotubesinfiltrated by the carbon may be configured to allow a second portion ofthe light that enters the through-channel at a second angle to passthrough from a top of the through-channel to a bottom of thethrough-channel.

In an example of the embodiment, the defined height to through-channelwidth aspect ratio may range from 3:1 to 10:1. The defined height tothrough-channel width aspect ratio may be 5:1. The set of aligned carbonnanotubes infiltrated by carbon may form the wall 808 with a thicknessranging from 1 micron to 50 microns and a height ranging from 50 micronsto 1000 microns.

FIG. 9A illustrates a ray diagram 900 of light 902 passing through amicrotube 904 and one or more layers of a miniaturized spectrometer suchas the first sensor 112, according to an embodiment. Some of thefeatures in FIG. 9A are the same as or similar to some of the featuresin FIGS. 1-8 as noted by same reference numbers, unless expresslydescribed otherwise. The layers may include the collimator 530 and/orthe filter 528. The microtube 904 may include a wall 906 and athrough-channel 908. The wall 906 may have a thickness 906 a and aheight 906 b. The thickness 906 a may range from 1 micron to 50 microns,from 1 micron to 20 microns, from 1 micron to 10 microns, and/or from 4microns to 5 microns. The height 906 b may range from 50 microns to 1000microns, from 100 microns to 900 microns, from 200 microns to 800microns, from 300 microns to 700 microns, from 400 microns to 600microns, from 450 microns to 550 microns, and/or from 225 microns to 275microns. In a specific embodiment the height 906 b may be 250 microns.The through-channel 908 may include a width 908 a. The width may rangefrom 10 microns to 300 microns, from 25 microns to 75 microns, from 40microns to 60 microns, from 45 microns to 55 microns, from 50 microns to250 microns, from 100 microns to 200 microns, and/or from 125 microns to175 microns. In a specific embodiment, the through-channel width 908 amay be 50 microns. The collimator 530 may include the filler 802.

In an embodiment, the wall thickness 906 a, the wall height 906 b, orthe through-channel width 908 a may form an aspect ratio of themicrotube 904. The aspect ratio may, for example, include a ratio of theheight 906 b to the through-channel width 908 a. The ratio may rangefrom 1:6 to 100:1, from 1:2.5 to 20:1, from 1:1 to 16:1, and/or from 2:1to 10:1. In an embodiment, the aspect ratio may be 5:1. In general, asthe through-channel width 908 a decreases, diffraction effects becomemore pronounced. However, as the aspect ratio increases, collimationincreases. Accordingly, a balance may be struck between increasingcollimation and decreasing diffraction. An aspect ratio which optimizesthis balance may be approximately 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1,and/or 10:1. In one embodiment, the optimal aspect ratio may be 5:1.

The dimensions of the collimator 530 may allow for incorporation of aspectrometer into a wearable device. A conventional spectrometer mayhave dimensions at least ranging upwards from multiple centimeterscubed. The size of a conventional spectrometer makes it impractical tointegrate into a wearable, such as a wristband, headband, arm band, andso forth. In contrast, the collimator 530 may have overall dimensionsranging less than a centimeter in length and less than or equal to 500microns thick (i.e. less than a thickness of 5 pieces of printer paper).When combined with an optical sensor such as the optical sensor 532 anda filter such as the filter 528, the elements may form a sensor, such asthe first sensor 112, having a thickness of less than or equal to 4 mm,less than or equal to 3.5 mm, and/or less than or equal to 3 mm.

The light 902 may impinge on the collimator 530 with an angle ofincidence θ_(incident). The filler 802 may refract the light 902 to anangle θ_(filler). The light 902 may pass through the through-channel 908and may impinge on the filter 528 at the angle θ_(filter). The filter528 may refract the light 902 to an angle θ_(filter). The angleθ_(incident), the angle θ_(filler), and/or the angle θ_(filter) may bedetermined according to Snell's Law, where the angle θ_(incident) maycorrespond to an index of refraction n_(incident), the angle θ_(filler)may correspond to an index of refraction n_(filler), and/or the angleθ_(filter) may correspond to an index of refraction n_(filter). Theindex of refraction n_(filler) may correspond to the material of thefiller 802. The index of refraction n_(filter) may correspond to thematerial of the filter 528. The index of refraction n_(incident) maycorrespond to a material adjacent to the collimator 530. In anembodiment, the material adjacent to the collimator 530 may include air.In an embodiment, the material adjacent to the collimator 530 mayinclude a polymer such as a flexible polymer. The flexible polymer mayhave a high transmissivity of the light 902, such as ranging from 80% to100% transmissivity of the light 902. The flexible polymer may be aportion of a band, such as the band 106 of the wearable device 100. Inan embodiment, the material adjacent to the collimator 530 may include abiological tissue. The tissue may be an epidermis, a dermis, a fattytissue, a muscular tissue, a connective tissue, a bone, and so forth.

FIG. 9B illustrates a ray diagram 920 showing a shadow effect of thecollimator 530 on light passing through the miniaturized spectrometer,according to an embodiment. Some of the features in FIG. 9B are the sameas or similar to some of the features in FIGS. 1-9A as noted by samereference numbers, unless expressly described otherwise. In anembodiment, the light 902 may enter the collimator 530 at a normal angleof incidence. For light 902 entering the collimator 530 at the normalangle of incidence where the angle θ_(incident) and/or the angleθ_(filler) may be equal to zero, a transmission efficiency I_(normal) ofthe collimator 530 may be proportional to the square of thethrough-channel width 908 a divided by a square of the through-channelwidth 908 a less the thickness 906 a of the microtube wall 906. Inembodiments where the collimator 530 includes a plurality of themicrotube 904, the transmission efficiency of the collimator 530 may bea mean, median, and/or mode of the transmission efficiency of various ofthe plurality of microtubes 904.

In an embodiment, the light 902 may enter the collimator 530 at anon-normal angle of incidence, which may create a shadow 910. The shadow910 may be a region adjacent to the microtube wall 906 through which nolight passes for a given θ_(incident) because light that would otherwisepass through the shadowed region is blocked by the microtube wall 906.The non-normal angle of incidence and resulting shadow 910 may reducetransmission efficiency of the collimator 530. Accordingly, the shadowedtransmission efficiency I_(shadow) of the collimator 530 may be zerowhen the shadow 910 is greater than the through-channel width 908 a,and/or may be proportional to the through-channel width 908 a less alength of the shadow 910, the result divided by the through-channelwidth 908 a. Using Snell's Law, the shadowed transmission efficiency ofthe collimator 530 may be determined using θ_(incident), the height 906b, and/or the refractive index n_(filler) of the filler. As θ_(incident)increases, the transmission efficiency of the collimator 530 may reduceto zero.

In an embodiment, the filter 528 may have a thickness that is a fractionof the wall height 906 b. For example, the filter 528 may include a thinfilm deposited on a substrate. The substrate may include a glasssubstrate, the substrate may include the collimator filler, and/or thesubstrate may include a photoreactive surface of the optical sensor 532.The filter thickness may be less than or equal to one tenth of the wallheight. For example, the filter may have a thickness ranging from 10 nmto 100 nm. Accordingly, a shadow on the optical sensor 532 due toadditional travel of the light through the filter 528 may be negligiblerelative to the shadow 910 on the filter 528 when calculating atransmission efficiency for the filter. In another embodiment, thefilter 528 may have a thickness relative to the wall height that mayrender the difference between the shadow on the optical sensor and theshadow 910 non-negligible due to the filter 528 thickness. For example,the filter thickness may be greater than one tenth of the wall height. Areduction in the transmission efficiency of the filter 528 due toenhancement of the shadow created by the wall 906 b may be determinedsimilar to I_(shadow).

In various embodiments, the reduction in transmission efficiency of thefilter 528 due to enhancement of the shadow created by the wall 906 bmay be negated by a thick filter 528. Light which may have passed from aneighboring microtube may strike an area of the optical sensor 532 whichmay have otherwise been shadowed by the wall 906 b. This may occur whenthe filter 528 is sufficiently thick to allow the light to travel farenough to bleed over from one microtube to the neighboring microtube.

FIG. 10A illustrates a ray diagram that correlates a gap 1002 a betweenthe collimator 530 and the optical sensor 532 with a region on theoptical sensor 532 the light 902 will strike, according to anembodiment. Some of the features in FIG. 10A are the same as or similarto some of the features in FIGS. 1-9B as noted by same referencenumbers, unless expressly described otherwise. A first segment 1008 a ofthe optical sensor 532 aligned with the microtube 904 may be identifiedby a processing device coupled to the optical sensor 532 as detectingwavelengths within a range corresponding to a range of unfiltered light902 that may pass through the microtube 904. The collimator 530 may beseparated from the optical sensor 532 by a distance 1002. For example,the filter 528 may be disposed between the collimator 530 and theoptical sensor 532, and the distance 1002 may include a thickness of thefilter 528. In another example, the filler 802 may surround themicrotube 904, and a portion of the filler 802 may be disposed betweenthe microtube 904 and the optical sensor 532. The distance 1002 mayinclude a thickness of the filler 802 disposed between the microtube 904and the optical sensor 532.

A material disposed between the microtube 904 and the optical sensor 532may have a refractive index n_(gap), where “gap” may generically referto any material disposed between the collimator 530 and the opticalsensor 532. The refractive index may be the same as or different thanthe index of refraction n_(filler). In various embodiments, light 902having a non-normal incidence on the filler 802 may pass into thematerial disposed between the microtube 904 and the optical sensor 532at an angle θ_(gap), which may correspond to the index of refractionn_(gap). In an embodiment where n_(gap) is equal to n_(filler), theangle θ_(gap) may be equal to the angle θ_(filler). In an embodimentwhere n_(gap) is less than n_(filler), the angle θ_(gap) may be greaterthan the angle θ_(filler). In an embodiment where n_(gap) is greaterthan n_(filler), the angle θ_(gap) may be less than the angleθ_(filler).

The light 902 may pass through the microtube 904 from a top edge of thewall 906 to a bottom edge 1006 of the wall 906. In various embodiments,n_(gap) may be less than n_(filler). The light 902 may be refracted asit passes from the filler 802 towards a second sensor segment 1008 b. Inan embodiment having a first length of the distance 1002, the light 902may strike the first sensor segment 1008 a. In an embodiment having asecond length of the distance 1002, the second length being greater thanthe first length, the light 902 may strike the second sensor segment1008 b. This may cause the processing device to identify the light 902as having a wavelength and/or range of wavelengths associated with thesecond sensor segment 1008 b, whereas the light 902 may actually have awavelength and/or range of wavelengths associated with the first sensorsegment 1008 a. In various embodiments, n_(gap) may be equal ton_(filler). In an embodiment having the first length of the distance1002, the light 902 may strike the first sensor segment 1008 a. In anembodiment having the second length of the distance 1002, the light 902may strike the second sensor segment 1008 b. In various embodiments,n_(gap) may be greater than n_(filler). The light 902 may be refractedas it passes from the filler 802 towards the first sensor segment 1008b. The light 902 may strike the first sensor segment 1008 a in anembodiment having the first length of the distance 1002 and in anembodiment having the second length of the distance 1002.

FIG. 10B illustrates a ray diagram 1020 that correlates the gap 1002 abetween the filter 528 and the sensor 532 with the region on the sensor532 the light 902 may impinge, according to an embodiment. Some of thefeatures in FIG. 10B are the same as or similar to some of the featuresin FIGS. 1-10A as noted by same reference numbers, unless expresslydescribed otherwise. A first segment 1008 a of the optical sensor 532aligned with the first filter region 528 a may be identified by aprocessing device coupled to the optical sensor 532 as detectingwavelengths within a range corresponding to a range of unfiltered light902 that may pass through the first filter region 528 a. The filter 528may be separated from the optical sensor 532 by a distance 1002. Forexample, the collimator 530 may be disposed between the filter 528 andthe optical sensor 532, and the distance 1002 may include a thickness ofthe collimator 530. In another example, the filter 528 may be aninterference filter which may include a filtering surface 1004 a and afilter substrate 1004 b. The filtering surface 1004 a may include a thinfilm that may transmit a wavelength or range of wavelengths whilereflecting other wavelengths. The filter substrate 1004 b may betransparent to the transmitted wavelength or range of wavelengths andthe other wavelengths. The filtering surface 1004 a may be depositedand/or adhered to the filter substrate 1004 b. The filter substrate 1004b may provide a rigid support structure for the filtering surface 1004a, as the filter substrate 1004 b may have a thickness many tens orhundreds of times a thickness of the filtering surface 1004 a.

The distance 1002 between the filtering surface 1004 a and the opticalsensor 532 may determine whether the light 902 having non-normalincidence on the filter 528 and passing though the first filter region528 a may strike the first sensor segment 1008 a or the second sensorsegment 1008 b. For a fixed angle of incidence on the filterθ_(incident) and fixed refractive indices n_(filter) and n_(gap) (where“gap” may refer to any material and/or space disposed between the filtersurface 1004 a and the optical sensor 532), the light 902 may strike thefirst sensor segment 1008 a for a first value of the distance 1002 andmay strike the second sensor segment 1008 b for a second value of thedistance 1002. A maximum value for the distance 1002 between the filtersurface 1004 a and the optical sensor 532 where the light 902 of fixednon-normal incidence may pass through the first filter region 528 a andstrike the first sensor segment 1008 a may be d_(max). A maximum valuefor θ_(incident) may be determined by various dimensions of thecollimator 530, such as the height 906 b of the microtube wall 906and/or the width 908 a of the through-channel 908. d_(max) may vary withthe maximum value for θ_(incident) and with varying values of n_(filter)and n_(gap).

In various embodiments, the processing device may correlate the firstsensor segment 1008 a with the first filter region 528 a and the secondsensor segment 1008 b with the second filter region 528 b. To ensurethat light passing through the filter surface 1004 a strikes the correctsensor segment, d_(max) may be minimized. In one embodiment, the filtersurface 1004 a may be placed against the optical sensor 532. In anotherembodiment, the filter surface 1004 may be integrated with the opticalsensor 532. For example, the optical sensor 532 may include aphotodiode, and the filter surface 1004 a may be deposited on thephotodiode. In such an embodiment, the filter surface 1004 may be anarrowband filter and/or a discrete wavelength filter. In oneembodiment, the collimator 530 may be positioned between the filter 528and the optical sensor 532 and the filter surface 1004 a may be placedagainst the collimator 530 facing the optical sensor 532. The collimator530 may function to ensure that rays of the light 902 passing throughthe first filter region of 528 a strike the first sensor segment 1008 aand may absorb and/or reflect rays of the light 902 passing through thefirst filter region 528 a that may have a trajectory to strike thesecond sensor segment 1008 b.

FIG. 10C illustrates an orientation and structure of the collimator 530relative to the optical sensor 532 that may reduce and/or eliminatecrossing of light to a neighboring sensor segment, according to anembodiment. Some of the features in FIG. 10C are the same as or similarto some of the features in FIGS. 1-10B as noted by same referencenumbers, unless expressly described otherwise. Where FIGS. 10A-B mayillustrate side-view diagrams, FIG. 10C may illustrate a top-viewschematic. In an embodiment, a filter, such as the filter 528 describedregarding FIGS. 10A-B, may be disposed between the collimator 520 andthe optical sensor 532. The filter may have a constant filteringfunction in a direction 1010 and may have a changing filtering functionin a direction 1012. The constant filtering function may filter lightalong an indicated direction in a constant manner. For example, thefilter may have the same passband at each point on the filter along theindicated direction corresponding to the constant filter function. Thechanging filtering function may filter light along an indicateddirection in a changing manner. For example, the filter may have adifferent passband at each point on the filer along the indicateddirection corresponding to the changing filter function. The thicknessof the wall 906 may be greater for wall 906 aligned with the direction1010 than for walls 906 aligned with the direction 1012.

In various embodiments, varying the thickness of the wall 906 may havesimilar effects to varying the distance 1002 described and/orillustrated regarding FIGS. 10A-B. Increasing the thickness of the wall906 may reduce the width of the through-channel relative to a width ofthe first sensor segment 1008 a. The reduced through-channel width maycompensate for n_(gap) (where “gap” may refer to material positionedbetween the collimator 530 and the optical sensor 532) being less thann_(filler), and/or for the distance between collimator 530. Light, suchas the light 902 described regarding FIGS. 10A-B, may be refractedtowards the second sensor segment 1008 b, but because thethrough-channel width is narrower due to the increased thickness of thewall 906, the light may strike the first sensor segment 1008 a. Invarious embodiments, the thickness of the wall 906 may directlycorrespond to the distance between the collimator 530 and the opticalsensor 532 to ensure light passing through the microtube 904 having agreatest angle θ_(filler) that may pass through the microtube 904 maystrike the first sensor segment 1008 a.

FIG. 11A is a picture of a section of the collimator 530, according toan embodiment. Some of the features in FIG. 11A are the same as orsimilar to some of the features in FIGS. 1-10C as noted by samereference numbers, unless expressly described otherwise. The collimator530 includes the wall 906 formed around the through-channel 908 to forma microtube. The wall may have a thickness ranging from 4 microns to 5microns. The through-channel 908 may have a width ranging from 50microns to 51 microns.

FIG. 11B illustrates a side view of a cross-section of the wall 906 ofthe microtube 904, showing an internal structure of the wall 906,according to an embodiment. Some of the features in FIG. 11B are thesame as or similar to some of the features in FIGS. 1-11A as noted bysame reference numbers, unless expressly described otherwise. The wall906 may define the through-channel 908 of the microtube 904. The wall906 may be formed of a nanotube forest 1102. The nanotube forest 1102may be grown along the height 906 b of the wall 906. The nanotube forest1102 may have a density which may be measured as a ratio of a volume inthe nanotube forest 1102 occupied by nanotubes to a volume of space inthe nanotube forest 1102 between the nanotubes. In an embodiment, theratio may be less than or equal to 1 percent. The ratio may becontrolled by varying a particle size of a catalyst used to grow thenanotube forest 1102. A bolstering material may be infiltrated into thespace between the nanotubes, such as the bolstering material describedregarding FIG. 7A. The bolstering material may, in an embodiment, fillthe space between the nanotubes. In an embodiment, the space between thenanotubes may include the bolstering material and voids. The voids maybe devoid of material, or the voids may include gas molecules. Invarious embodiments, after infiltration, 80 percent to 90 percent of thevolume in the nanotube forest may be occupied by the bolsteringmaterial.

FIG. 11C illustrates a picture from a perspective view of the collimator530, according to an embodiment. Some of the features in FIG. 11C arethe same as or similar to some of the features in FIGS. 1-11B as notedby same reference numbers, unless expressly described otherwise. In aspecific embodiment, the collimator 530 may have a height ofapproximately 425 microns and a through-channel width of approximately10 microns. Accordingly, the aspect ratio may be 42.5:1.

FIG. 12A is a top-side picture of the collimator 530 showing the wall906 and the through-channel 908 of the microtube 904, according to anembodiment. Some of the features in FIG. 12A are the same as or similarto some of the features in FIGS. 1-11C as noted by same referencenumbers, unless expressly described otherwise. The collimator 530 mayinclude a plurality of the microtube 904. The wall 906 of the microtube904 may have a thickness ranging from 3 microns to 5 microns. In anembodiment, the wall 906 may have a thickness of 4 microns. Thethrough-channel 908 of the microtube 904 may have a width ranging from90 microns to 110 microns. In an embodiment, the through-channel 908 mayhave a width of 100 microns.

FIG. 12B is a picture of a diffraction pattern 1200 of light collimatedby the collimator 530 at 10 mm from the collimator 530, according to anembodiment. Some of the features in FIG. 12B are the same as or similarto some of the features in FIGS. 1-12A as noted by same referencenumbers, unless expressly described otherwise. As the light passes fromone of the plurality of the microtubes 904, a wave pattern of the lightmay spread spatially to a region adjacent to an opening of a neighboringmicrotube 904. As a width of the through-channel decreases relative to awavelength of the light passing through the through-channel 908,diffraction of the light as it leaves the through-channel 908 may affectan intensity of the light measured at the optical sensor. Diffractionmay, in some embodiments, result in a significant amount of theintensity of the light being diffracted to an area outside a regiondirectly beneath the collimator 530. However, in some embodiments, thethrough-channel width may be tuned to maximize collimation and minimizediffraction. In various embodiments the tuning may relate to the aspectratio of the microtube 904 and/or the wavelengths of light beingcollimated. A higher aspect ratio may result in better collimation,whereas a larger through-channel width 908 may minimize diffraction. Inone embodiment, for a through-channel width of 100 microns, diffractionof 700 nm-wavelength light may result in over 95% of the intensity ofthe light falling beneath the collimator 530.

FIG. 13 shows a graph 1300 illustrating an intensity profile of thediffraction pattern 1200 illustrated in FIG. 12B. Some of the featuresin FIG. 13 are the same as or similar to some of the features in FIGS.1-12B as noted by same reference numbers, unless expressly describedotherwise. The dashed lines 1302 may illustrate positions ofthrough-channels of the collimator 530. The collimator 530 may have athrough-channel width of 100 microns. At line 1304 the intensity of thelight is null, and at line 1306 the intensity of the light is 100% ofthe intensity of the light as the light passes out of the collimator530. Peaks and valleys of a curve 1310 indicate higher intensity andlower intensity, respectively, at a corresponding location beneath thecollimator 530. Accordingly, some areas have greater intensity than theintensity of the light as it passed out of the collimator 530, whereasother areas have less intensity than the intensity of the light as itpassed from the collimator 530. A sum of the intensities at each pointunder the collimator 530 may be, in an embodiment, approximately 95% ofthe intensity of the light is it passed from the collimator 530. Thecurve 1310 indicates that, in an embodiment, diffraction does not resultin significant attenuation of the light beneath the collimator for a 100micron through-channel width.

FIG. 14A shows a graph 1402 illustrating transmission curves 1402 a-ccorresponding to various refractive indices for collimated anduncollimated light, according to an embodiment. Some of the features inFIG. 14A are the same as or similar to some of the features in FIGS.1-13 as noted by same reference numbers, unless expressly describedotherwise. The transmission curves 1402 a-c may correspond to broadbandlight having wavelengths ranging from 560 nm to 840 nm passed through afilter, such as the filter 528. The filter may be a bandpass filter,such as a Fabry-Perot etalon filter. The filter may be a 700 nm bandpassfilter. The broadband light may be incident on a collimator at variousangles θ_(incident) ranging from −60 degrees)(° from normal to 60° fromnormal. The collimator may, for example, include the collimator 530described and illustrated regarding other FIGs. herein.

In an embodiment, the transmission curves 1402 a-c may be modeledaccording to a numerical relationship I_(filter) between an effectivewavelength λ_(eff) of light passing through the filter and a wavelengthλ₀ of peak transmission through the filter. The I_(filter) may bemodeled as

$I_{filter} = {{0.6{\exp\left( {- \frac{❘{\lambda_{eff} - \lambda_{0}}❘}{2\left( {{0.0}03\lambda_{0}} \right)^{2}}} \right)}} + {0.3{{\exp\left( {- \frac{\left| {\lambda_{eff} - \lambda_{0}} \right|}{2\left( {{0.0}2\lambda_{0}} \right)^{2}}} \right)}.}}}$In an embodiment, λ_(eff) may be an effective wavelength of lightpassing through the filter based on the angle θ_(incident) at which thelight is incident on the collimator. For example, the filter may be aFabry-Perot filter. The mechanism of the filter may be destructiveinterference. A first wave that may experience a same and/or similarphase transition as a second wave may have a similar attenuation by thefilter as the second wave. Accordingly, the λ_(eff) may be modeled as

${\lambda_{eff} = \frac{\lambda_{incident}}{\cos\left( {{arc}{\sin\left( \frac{\sin\theta_{incident}}{n_{filter}} \right)}} \right)}},$

where λ_(incident) may be a wavelength of the light incident on thefilter. As the angle θ_(incident) increases, λ_(eff) may decrease sothat a longer wavelength may be filtered by the filter as if thewavelength were shorter.

For example, the filter may have a passband with a 700 nm peak and aFWHM band ranging from 675 nm to 725 nm for broadband light striking thefilter at a normal θ_(incident). A shape of a curve modeling thepassband for normally-incident broadband light may be symmetric aboutthe peak. However, for non-normally-incident broadband light, a shape ofthe curve such as the transmission curve 1402 a may be asymmetric abouta peak of the transmission curve 1402 a. The asymmetry may be due to anincrease in an apparent intensity of lower-wavelength light due to theeffects on non-normal incidence. The apparent intensity may be anintensity of the wavelength after the light passes through the filterand may be different than an intensity of the wavelength before thelight passes through the filter. Accordingly, wavelengths larger thanthe peak-transmission wavelength may have a lower apparent intensity.The peak-transmission wavelength may have a lower apparent intensity. Awavelength shorter than the peak-transmission wavelength may appear tobe the peak-transmission wavelength. The peak-transmission wavelengthmay have a higher apparent intensity. Wavelengths smaller than thepeak-transmission wavelength may have a higher apparent intensity. Forexample, a FWHM band of the transmission curve 1402 a may range from 665nm to 705 nm, and the apparent peak-transmission wavelength of thetransmission curve 1402 a may be 695 nm.

The asymmetry and/or shift of the transmission curve 1402 a fornon-normally-incident light may indicate that the filter may transmit ahigher total intensity of light than an intensity of the light thatcorresponds to the filter passband. This may cause a sensor, such as theoptical sensor 532, communicate an incorrect intensity of the light to aprocessing device, which may in turn incorrectly interpret thecommunicated intensity. For example, the processing device may interpretthe communicated intensity to correspond to an incorrect physiologicalcondition, physiological parameter, and/or physiological constituent. Invarious embodiments, the processing device may compensate for theasymmetry and/or shift of the transmission curve 1402 a. For example,the processing device may store information regarding the intensityand/or a spectral profile of the light before the light passes throughthe filter. The processing device may, based on the intensity and/orspectral profile of the light before the light passes through thefilter, adjust an intensity communicated to the processing device by theoptical sensor. However, in various embodiments, it may be impractical,inconvenient, and/or unlikely to have information regarding the lightbefore the light passes through the filter, such as when the lightpasses through another material and an intensity of at least onewavelength of the light is attenuated. For example, the light may passthrough a tissue of a body part before passing through the filter.

In an embodiment, the collimator may reduce and/or eliminate theasymmetry and/or shift of the transmission curve 1402 a, as may beillustrated by the transmission curve 1402 b and/or the transmissioncurve 1402 c. The transmission curve 1402 b may correspond to collimatedlight, where the collimator includes a filler, such as the filler 802,having a refractive index n_(filler) equal to 1. The transmission curve1402 b may correspond to collimated light, where the collimator includesthe filler having a refractive index n_(filler) equal to 2. A wall ofthe collimator, such as the wall 906, may have a height, such as theheight 906 a, equal to 250 microns, and/or may have a thickness, such asthe thickness 906 b, equal to 5 microns. A through-channel formed by thewall, such as the through-channel 908, may have a width, such as thewidth 908 a, equal to 50 microns.

A difference between the transmission curve 1402 b and the transmissioncurve 1402 c may correspond to a difference between n_(filler) for thetransmission curve 1402 b and n _(filler) for the transmission curve1402 c. As n_(filler) increases, a percentage of the light reflected atsurfaces of the filler (i.e. at interfaces between the collimator andthe filter, the optical sensor, open air, a surface against which thecollimator is placed, and so forth) also increases. Conversely, asn_(filler) increases, θ_(filler) for non-normal light may decrease. Thedecreasing θ_(filler) may have an effect similar to widening themicrotube through-channel. Because θ_(filler) decreases, less light maybe reflected and/or absorbed by the microtube walls, and more light maybe transmitted through the through-channel. The difference between thetransmission curve 1402 b and the transmission curve 1402 c may indicatethat the effect of the decreasing θ_(filler) may weigh more heavily inthe difference than the effect of the increasing reflection.Accordingly, as n_(filler) increases, the collimator may transmit morelight. In various embodiments, n_(filler)—may range from 1.3 to 1.7.

The collimator may limit the angle θ_(incident) to a smaller range ofangles, which may in turn limit a maximum path length of lighttransmitted through the filter. The collimator may reduce an average ofthe path lengths of the light transmitted through the filter byabsorbing and/or reflecting away from the filter and/or the opticalsensor light rays having an angle θ_(incident) larger than an arctangentof a ratio of the wall height to the through-channel width. The reducedrange of the angle θ_(incident) may narrow a range of the effectivewavelengths λ_(eff). The reduced range of λ_(eff) may narrow thetransmission curve and/or may render the transmission curve moresymmetrical compared to the transmission curve 1402 a, as may beillustrated by the transmission curve 1402 b and the transmission curve1402 c.

In various embodiments, the filter, the collimator, and/or the opticalsensor may be integrated into a miniaturized spectrometer. Factors suchas shadowing, an amount of light transmitted through the filter, and/orreflection of light at layer interfaces may affect an intensity of thelight detected by the optical sensor I_(sensor). Additionally, variouslayers and/or materials of the collimator and/or the filter may absorbsome energy of the light as the light is transmitted through thecollimator and/or the filter. Accordingly, I_(sensor) may be modeled asa product of I_(filter), I_(normal), I_(shadow), and/or I_(trans).

Factors such as I_(filter), I_(normal), I_(shadow), and/or I_(trans) maybe stored to be accessible by the processing device, and the processingdevice may use the factors in processing light intensities communicatedby the optical sensor to the processing device. For example, a broadbandlight source may emit the light towards a body part of a user of awearable device, such as the wearable device 100. The light may passinto the body part. Various wavelengths of the light may be reflected,refracted, and/or absorbed by one or more constituents of the body part.Features of light leaving the body part, such as the intensity and/orthe spectral profile of the light, may correspond to one or morephysiological conditions, physiological parameters, and/or physiologicalconstituents of the user. The light may pass from the body part to theminiaturized spectrometer. The collimator may collimate the light. Thefilter may filter the light. The optical sensor may generate a signalcorresponding to an intensity of the collimated and/or filtered lightimpinging on the optical sensor. The signal may be transmitted to theprocessing device. The processing device may determine an intensity ofthe light impinging on the optical sensor based on the signal. Theprocessing device may determine a spectral profile of the lightimpinging on the optical sensor based on the signal.

The processing device may access information about the light emittedfrom the light source, such as the intensity and/or spectral profile ofthe light. For example, the information may be communicated from thelight source to the processing device, and/or the information may bestored on a memory device electronically coupled to the processingdevice. The processing device may calculate a maximum possible intensityof the light impinging on the optical sensor based on I_(sensor) and/orthe intensity of the light emitted from the light source. The processingdevice may compare the intensity and/or the spectral profile of thelight impinging on the optical sensor to the maximum possible intensityof the light, the intensity of the light emitted from the light source,and/or the spectral profile of the light emitted from the light source.Based on the comparison, the processing device may determine aphysiological condition, physiological parameter, and/or a physiologicalconstituent of the user.

FIG. 14B shows a graph 1404 illustrating transmission curves 1404 a-dcorresponding to various through-channel widths for collimated anduncollimated light, according to an embodiment. Some of the features inFIG. 14B are the same as or similar to some of the features in FIGS.1-14A as noted by same reference numbers, unless expressly describedotherwise. The transmission curves 1404 a-d may correspond to broadbandlight having wavelengths ranging from 560 nm to 840 nm passed through afilter. In an embodiment, the filter may be the filter 528 described andillustrated herein. The filter may be a bandpass filter. For example,the filter may be a Fabry-Perot etalon filter. The filter may be a 700nm bandpass filter. The broadband light may be incident on a collimatorat various angles θ_(incident) ranging from −60 degrees)(° from normalto 60° from normal. In an embodiment, the collimator may be thecollimator 530 described and illustrated herein.

The transmission curve 1404 a may correspond to uncollimated light. Thetransmission curves 1404 b-d may correspond to collimated light. Thecollimator may include a wall, such as the wall 906, having a height,such as the height 906 b, equal to 250 microns. A thickness of the wall,such as the thickness 906 a, may be equal to 5 microns. The wall mayform a microtube, such as the microtube, having a through-channel, suchas the through-channel 908 a. The through-channel may be filled with afiller, such as the filler 802. The filler may have an index ofrefraction n_(filler) equal to 1. The through-channel may have a width,such as the width 908 a. The transmission curve 1404 b may correspond toa width of the through-channel equal to 40 microns. The transmissioncurve 1404 c may correspond to a width of the through-channel equal to80 microns. The transmission curve 1404 d may correspond to a width ofthe through-channel equal to 180 microns.

In an embodiment, an aspect ratio of the microtube and/or the collimatormay be a ratio of the wall height to the through-channel width. Theaspect ratio may correspond to a range of incident angles θ_(incident)for light that may be transmitted through the collimator. In anembodiment, increasing the aspect ratio of the microtube and/or thecollimator may narrow a range of angles θ_(incident) for which lightincident on the collimator may pass through the microtube and/or thecollimator. In an embodiment, increasing the aspect ratio of themicrotube and/or the collimator may narrow a FWHM band of a transmissioncurve corresponding to light passing through the collimator and/ormicrotube. In an embodiment, increasing the aspect ratio of themicrotube and/or the collimator may reduce I_(shadow). In anotherembodiment, decreasing the aspect ratio of the microtube and/or thecollimator may broaden the range of angles θ_(incident) for which lightincident on the collimator may pass through the microtube and/or thecollimator, and/or may broaden the FWHM band of the transmission curve.However, above a threshold aspect ratio, the transmission curve maybecome asymmetric similar to the transmission curve 1404 a foruncollimated light. The threshold aspect ratio may range from 1 to 10,from 1 to 8 from 2 to 5, and/or from 3 to 4. In one embodiment, thethreshold aspect ratio may be 3.125.

In an embodiment, the transmission curve 1404 b may have an aspect ratioof 6.250. The transmission curve 1404 b may be symmetric about its peak.In an embodiment, the transmission curve 1404 c may have an aspect ratioof 3.125. The transmission curve 1404 c may be symmetric about its peak.In an embodiment, the transmission curve 1404 d may have an aspect ratioof 1.389. The transmission curve 1404 d may be asymmetric about itspeak. As may be illustrated by a comparison of the transmission curves1404 b-d with the transmission curves 1402 b-c, variation of thetransmission curves may be more significant as the aspect ratio isvaried than as the refractive index n_(filler) is varied.

The transmission curves 1402 a-c described and illustrated regardingFIG. 14A and the transmission curves 1404 a-d described and illustratedregarding FIG. 14B may illustrate how the collimator may enablemeasurement by a miniaturized spectrometer. A conventional spectrometermay include a lens and/or mirrors to collimate light. Accordingly, aconventional spectrometer may be too bulky to incorporate into awearable device. The collimator described herein may allow for compactenough construction of the miniaturized spectrometer to integrate intothe wearable device, and more particularly into the band of the wearabledevice, where space may be more limited than in, for example, a watchhead of the wearable device. The transmission curve 1402 a and thetransmission curve 1404 a may illustrate that a miniaturizedspectrometer operating without the collimator may have skewedmeasurements, lower resolution measurements, and/or otherwise incorrectmeasurements. The transmission curves 1402 b-c and the transmissioncurves 1404 b-d may illustrate that a miniaturized spectrometeroperating with the collimator may more accurately measure relativewavelength intensities than the miniaturized spectrometer operatingwithout the collimator.

The transmission curves 1402 b-c and the transmission curves 140 b-d mayfurther demonstrate that dimensions of the collimator may be tuned for aparticular application. For example, in one application, high resolutionmay be preferred over high sensitivity. Accordingly, dimensionsproducing the transmission curve 1402 b and/or the transmission curve1404 b may be preferred over other dimensions. In another application,high sensitivity may be preferred over high resolution. Accordingly,dimensions producing the transmission curve 1402 c and/or thetransmission curve 1404 d may be preferred over other dimensions. In yetanother application, a balance between resolution and sensitivity may beoptimized. Accordingly, dimensions producing the transmission curve 1404c may be preferred over other dimensions.

FIG. 15A is a graph 1502 illustrating a transmission efficiency of amicrotube having a wall with a 250 micron height and a through-channelwith a 25 micron width, according to an embodiment. Some of the featuresin FIG. 15A are the same as or similar to some of the features in FIGS.1-14B as noted by same reference numbers, unless expressly describedotherwise. The graph plots transmission percentage of light for a rangeof angels from −30° to 30°. The graph includes a model-generated curve1502 a and an experimentally generated curve 1502 b. The model-generatedcurve 1502 a may have been generated using the model for I_(sensor)described herein. The experimentally generated curve 1504 b may includedirect measurements taken using embodiments of a light source such asthe light source 602, a collimator such as the collimator 530, a filtersuch as the filter 528, and/or an optical sensor such as the opticalsensor 532. The light source 602 may include a tungsten filament bulb.The fliter 528 may include a monochromator selectively set to 1550 nm.

The model-generated curve 1502 a may have a peak transmission efficiencyranging from 70 percent to 80 percent for zero-degree incidence. In oneembodiment, the model-generated curve 1502 a may have a peaktransmission efficiency of 74.3% The model-generated curve 1502 a mayhave non-zero transmission ranging from −6° to 6° and may be symmetricalabout the peak transmission efficiency. In one embodiment, themodel-generated curve 1502 a may have non-zero transmission ranging from−5.71° to 5.71°. The experimentally generated curve 1502 b may have aglobal peak transmission efficiency ranging from 20 percent to 30percent for zero-degree incidence and two local peaks fornon-zero-degree incidence. In one embodiment, the experimentallygenerated curve 1502 b may have a global peak transmission efficiency of23.8 percent. The non-zero-degree incidence local peaks may correspondto diffraction effects of the collimator. The experimentally generatedcurve 1502 b may have a non-zero transmission ranging from −6° to 6°and/or from −4° to 4°. In one embodiment, the experimentally generatedcurve 1502 b may have a non-zero transmission ranging from −5.58° to4.22°.

FIG. 15B is a graph 1504 illustrating a transmission efficiency of amicrotube having a wall with a 250 micron height and a through-channelwith a 50 micron width, according to an embodiment. Some of the featuresin FIG. 15B are the same as or similar to some of the features in FIGS.1-15A as noted by same reference numbers, unless expressly describedotherwise. The graph includes a model-generated curve 1504 a and anexperimentally generated curve 1504 b. The model-generated curve 1504 amay have been generated using the model for I_(sensor) described herein.The experimentally generated curve 1504 b may include directmeasurements taken using embodiments of a light source such as the lightsource 602, a collimator such as the collimator 530, a filter such asthe filter 528, and/or an optical sensor such as the optical sensor 532.The model-generated curve 1504 a may have a peak transmission efficiencyranging from 80 percent to 90 percent for zero-degree incidence. In oneembodiment, the model-generated curve 1504 a may have a peaktransmission efficiency of 85.7 percent. The model-generated curve 1504a may have non-zero transmission ranging from −15° to 15° and may besymmetrical about the peak transmission efficiency. In one embodiment,the model-generated curve 1504 a may have a non-zero transmissionranging from −11.3° to 11.3°. The experimentally generated curve 1504 bmay have a global peak transmission efficiency ranging from 40 percentto 45 percent for zero-degree incidence with no local peaks. In oneembodiment, the experimentally generated curve 1504 b may have a globalpeak transmission efficiency of 42.9 percent. The experimentallygenerated curve 1504 b may have a non-zero transmission ranging from−16° to 16° and/or from −10° to 10°. In one embodiment, theexperimentally generated curve 1504 b may have a non-zero transmissionranging from −10.2° to 9.16°.

FIG. 15C is a graph 1506 illustrating a transmission efficiency of amicrotube having a wall with a 250 micron height and a through-channelwith a 100 micron width, according to an embodiment. Some of thefeatures in FIG. 15C are the same as or similar to some of the featuresin FIGS. 1-15B as noted by same reference numbers, unless expresslydescribed otherwise. The graph includes a model-generated curve 1506 aand an experimentally generated curve 1506 b. The model-generated curve1506 a may have been generated using the model for I_(sensor) describedherein. The experimentally generated curve 1506 b may include directmeasurements taken using embodiments of a light source such as the lightsource 602, a collimator such as the collimator 530, a filter such asthe filter 528, and/or an optical sensor such as the optical sensor 532.The model-generated curve 1506 a may have a peak transmission efficiencyranging from 90 percent to 95 percent for zero-degree incidence. In oneembodiment, the model-generated curve 1506 a may have a peaktransmission of 92.5 percent. The model-generated curve 1506 a may havenon-zero transmission ranging from −25° to 25° and may be symmetricalabout the peak transmission efficiency. In one embodiment, themodel-generated curve 1506 a may have a non-zero transmission rangingfrom −21.8° to 21.8°. The experimentally generated curve 1506 b may havea global peak transmission efficiency ranging from 65 percent to 70percent for zero-degree incidence with no local peaks. In oneembodiment, the experimentally generated curve 1506 b may have a globalpeak transmission efficiency of 68.2 percent. The experimentallygenerated curve 1506 b may have a non-zero transmission ranging from−20° to 20° and/or −24° to 24°. In one embodiment, the experimentallygenerated curve 1506 b may have a non-zero transmission ranging from−20° to 20.6°.

A comparison of the graphs 1502, 1504, and/or 1506 may show themodel-generated curves match the experimentally generated curves betterfor wider through-channels. Accordingly, changing the through-channelwidth may have a different experimental relationship with angle ofincidence and/or transmission efficiency than the modeled relationship.Additionally, the graphs 1502, 1504, and/or 1506 show close correlationbetween model and experiment where transmission reaches 0 percent, whichdemonstrates the collimator is highly absorptive at the wavelength ofinterest. Furthermore, a comparison of the difference between theexperimental results and the modeled results as microtube with increasesshows that diffraction effects play a larger role for smaller microtubewidths than for larger microtube widths. The modeled curves 1502 a, 1504a, and 1506 a do not include diffraction effects as part of the modelcalculation. However, the experimental curves 1502 b, 1504 b, and 1506 binclude reduction in transmission efficiency due to diffraction.Notably, diffraction may play a significantly larger role in reducingtransmission efficiency for microtube widths less than 100 microns.

The above description sets forth numerous specific details such asexamples of specific systems, components, methods and so forth, in orderto provide a good understanding of several implementations. It will beapparent to one skilled in the art, however, that at least someimplementations may be practiced without these specific details. Inother instances, well-known components or methods are not described indetail or are presented in simple block diagram format in order to avoidunnecessarily obscuring the present implementations. Thus, the specificdetails set forth above are merely exemplary. Particular implementationsmay vary from these exemplary details and still be contemplated to bewithin the scope of the present implementations.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many other implementations will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the present implementations should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled.

The disclosure above encompasses multiple distinct embodiments withindependent utility. While these embodiments have been disclosed in aparticular form, the specific embodiments disclosed and illustratedabove are not to be considered in a limiting sense as numerousvariations are possible. The subject matter of the embodiments includesthe novel and non-obvious combinations and sub-combinations of thevarious elements, features, functions and/or properties disclosed aboveand inherent to those skilled in the art pertaining to such embodiments.Where the disclosure or subsequently filed claims recite “a” element, “afirst” element, or any such equivalent term, the disclosure or claims isto be understood to incorporate one or more such elements, neitherrequiring nor excluding two or more such elements.

Applicant(s) reserves the right to submit claims directed tocombinations and sub-combinations of the disclosed embodiments that arebelieved to be novel and non-obvious.

Embodiments embodied in other combinations and sub-combinations offeatures, functions, elements and/or properties may be claimed throughamendment of those claims or presentation of new claims in the presentapplication or in a related application. Such amended or new claims,whether they are directed to the same embodiment or a differentembodiment and whether they are different, broader, narrower or equal inscope to the original claims, are to be considered within the subjectmatter of the embodiments described herein.

The invention claimed is:
 1. A device, comprising: a flexible bandconfigured to extend at least partially around a wrist of a user; a userinterface coupled to the flexible band; a processing device coupled theflexible band; a light source embedded in the flexible band, wherein thelight source is configured to: press against a dermal layer of the wristof the user by the flexible band as the user wears the flexible band;and emit light into an underside of the wrist as the user wears theflexible band; a miniaturized spectrometer integrated into the flexibleband, wherein: the miniaturized spectrometer is positioned in theflexible band and configured to: press against the dermal layer alongthe underside of the wrist as the user wears the flexible band; andreceive the light from the light source through the underside of thewrist or the muscular-walled tube as the user wears the flexible band;the miniaturized spectrometer comprises: a collimator, wherein: thecollimator comprises a microtube, the microtube comprising a walldefining a through-channel; the wall comprises a carbon nanotube forest,the carbon nanotube forest comprising a bundle of carbon nanotubesaligned approximately parallel with each other; an optical filterconfigured to have a passband corresponding to a wavelength of lightproviding an indication of a condition or constituent of the wrist, thedermal layer, or a muscular-walled tube within the wrist; and an opticalsensor, wherein the processing device or the optical sensor isconfigured to: identify the wavelength of light; and measure anintensity of the wavelength of light; at least two of the collimator,the optical filter, and the optical sensor are stacked together; and anelectrical trace integrated into the flexible band and electricallyinterconnecting the processing device, the user interface, the lightsource, or the optical sensor.
 2. The device of claim 1, furthercomprising a borosilicate glass stacked with the collimator, the opticalfilter, or the optical sensor, wherein the borosilicate glass is alignedflush with an inside surface of the flexible band, the inside surfacedesigned to face the wrist of the user as the user wears the flexibleband.
 3. The device of claim 1, wherein: identifying the wavelengthcomprises correlating a position on the optical sensor where the lightstrikes the optical sensor with a segment of the optical filter alignedwith the position on the optical sensor; and the segment of the opticalfilter comprises a passband for the wavelength.
 4. The device of claim1, wherein: the collimator is positioned in the stack and configured topress against the wrist as the user wears the flexible band, wherein thecollimator is positioned, as the user wears the flexible band, tocollimate the light to enable the light to strike a portion of theoptical sensor corresponding to a portion of the filter through whichthe light passed; or the filter is positioned in the stack andconfigured to press against the wrist as the user wears the flexibleband to enable filtered light to be collimated and passed to the portionof the optical sensor corresponding to the portion of the filter throughwhich the light passed.
 5. The device of claim 1, wherein the processingdevice is configured to determine a constituent of the muscular-walledtube based on the intensity of the wavelength.
 6. The device of claim 1,wherein: an inward-facing surface of the miniaturized spectrometer isflush with an inside surface of the flexible band; the inward-facingsurface of the miniaturized spectrometer is positioned in the flexibleband and configured to be pressed against the wrist of the user as theuser wears the flexible band to prevent outside light from outside thewrist from entering the miniaturized spectrometer or reaching theoptical sensor as the user wears the flexible band; the inward-facingsurface is configured to receive the light into the miniaturizedspectrometer through the wrist as the user wears the flexible band; andthe inside surface of the flexible band is configured to face the wristas the user wears the flexible band.
 7. The device of claim 1, whereinthe light source and the miniaturized spectrometer are positioned in theflexible band relative to each other to prevent light noise from beingdetected by the miniaturized spectrometer, wherein the light noisecomprises external light entering the miniaturized spectrometer fromoutside the wrist.
 8. The device of claim 1, wherein the light sourceand the miniaturized spectrometer are spaced from each other in theflexible band to prevent light emitted by the light source travelingoutside the wrist from being detected by the miniaturized spectrometeras the user wears the flexible band.
 9. The device of claim 1, whereinthe light source is recessed in the flexible band to prevent lightemitted by the light source from traveling outside the wrist as the userwears the flexible band.
 10. The device of claim 1, wherein the userinterface is coupled to the band and configured to be positioned on atop side of the wrist opposite the light source or the miniaturizedspectrometer as the user wears the flexible band.
 11. The device ofclaim 10, wherein the user interface is coupled to the flexible band ina position to orient the user to align the light source or theminiaturized spectrometer with the muscular-walled tube as the userwears the flexible band.
 12. A device, comprising: a band configured toextend at least partially around a body part of a user, the body partcomprising a dermal layer and a subdermal feature within the body part;a light source embedded in the band, wherein the light source isconfigured to emit light into the body part as the user wears the band;a miniaturized spectrometer integrated into the band, wherein theminiaturized spectrometer comprises: a collimator for collimating thelight, the collimator comprising a plurality of microtubes, wherein themicrotubes comprise carbon nanotube walls defining a plurality ofthrough-channels; an optical filter for filtering the light, the opticalfilter configured to have a plurality of passbands corresponding toconstituent wavelengths of the light; and an optical sensor configuredto detect intensities of the constituent wavelengths and communicate theintensities to a processing device, wherein the miniaturizedspectrometer is configured to: collimate the light; filter the lightinto relevant constituent wavelengths, wherein the relevant constituentwavelengths are reflected by or transmitted through the body part, thedermal layer, or the subdermal feature as the user wears the band; anddetect the intensities of the constituent wavelengths.
 13. The device ofclaim 12, wherein: the light source comprises a light-emitting portionflush with an inside surface of the band; and the inside surface of theband is configured to face the body part as the user wears the band; orwherein: a receiving surface of the miniaturized spectrometer is flushwith the inside surface of the band; the receiving surface is configuredto receive light into the miniaturized spectrometer through the bodypart as the user wears the band; and the inside surface of the band isconfigured to face the body part as the user wears the band.
 14. Thedevice of claim 12, further comprising a user interface, wherein theuser interface is coupled to the band to be adjacent to a side of thebody part opposite the light source or the miniaturized spectrometer asthe user wears the band.
 15. The device of claim 12, further comprisinga processing device configured to identify, as the user wears the band,a quantity of a constituent of the subdermal feature based on theintensities of the constituent wavelengths.
 16. The device of claim 12,wherein the light source and the miniaturized spectrometer are spacedfrom each other in the band to prevent light emitted by the light sourceand traveling outside the body part from being detected by theminiaturized spectrometer as the user wears the band.
 17. The device ofclaim 16, wherein: the band is configured to press the light source andthe miniaturized spectrometer into the wrist; or the light source andthe miniaturized spectrometer are recessed within the band.
 18. Adevice, comprising: a band configured to extend at least partiallyaround a body part of a user; a light source embedded in the band,wherein the light source is configured to emit light into an internalfeature within the body part as the user wears the band; and aminiaturized spectrometer positioned in the band and configured to pressagainst the body part to receive the light from the internal featurewithin the body part, the miniaturized spectrometer comprising: acollimator configured to collimate the light from the body part, whereinthe collimator comprises a microtube; an optical filter configured tofilter the light from the body part; and an optical sensor configured todetect an intensity of the light from the body part; wherein at leasttwo of the collimator, the optical sensor, and the optical filter arearranged together to form a stack embedded in the band.
 19. The deviceof claim 18, wherein: the collimator and the optical sensor are stackedtogether; the optical sensor is positioned in the stack to detect lightpassing through the body part as the user wears the band; the collimatoris positioned in the stack and configured to be between the opticalsensor and the body part as the user wears the band; the optical filteris positioned in the band adjacent to the light source; and the opticalfilter is positioned in the band and configured to be between the lightsource and the body part as the user wears the band.
 20. The device ofclaim 18, wherein: the light source comprises a light-emitting portionflush with an inside surface of the band; and the inside surface of theband is configured to face the body part as the user wears the band; orwherein: a receiving surface of the miniaturized spectrometer is flushwith an inside surface of the band; the receiving surface is configuredto receive light into the miniaturized spectrometer through the bodypart as the user wears the band; and the inside surface of the bandfaces the body part as the user wears the band.